It's not bad at all for a wifi based VOIP phone.setup is all via a GUI, and it is relatively straightforward.. Took only 2 or 3 minutes to connect with a FreePBX (asterisk) VOIP box, and it worked.audio quality is....well, it's Grandstream.. Not entirely sh**t... but not far from it. Of course that's the Grandstream we've come to know and love, right?the biggest complaint I have is the ergonomics of the buttons.. it's really got the typical cheap Chinese tech feel - buttons are sloppy, plastic is thin, etc..Most of the time you have press the buttons hard (or harder than you should need to), and almost every call, i find that i've miss-dialed a number or two because of it. I've configured dozens of Polycom Kirk systems (now called Spectralink), and the quality difference is night & day... a 10 year old Kirk phone sounds night & day better than the Grandstream, and the feel is well, professional vs bush-league...if i could convince VOIP clients to put up with the Spectralink handsets' "old" GUI, i'd never place these in... but it is cheap, fast, and quasi reliable...Been using this phone on its second day and it seems it works better with 2.4Ghz WiFi frequency. There’s little to no interefence and you can walk around with it. I haven’t tested carrying it for long since I work from home. Although it’s very convenient if you need to grab or do some stuff around the house with it. Plus it has a 3.5mm audio jack so you can just press the PTT button (I set it to mute button) if need be.As for the interface, it looks like a very basic cordless phone. Nothing fancy. Nothing bad with it. You can adjust the settings directly to the phone or use the web GUI.As for the lines. Yes, it can connect up to two lines only with transfer, hold, mute functionalities. You can switch between lines if you need to call with either accounts. You just need to press the Accounts soft key for this. It also has an alarm and calculator which is handy sometimes.The look and feel seems better than a China phone to be honest. I’ve seen a lot of China phones and I have no issues with its design. It’s a very basic phone like one of those Nokia 5210 models but taller.This is my first Grandstream phone and I’m fine with it. If you can’t carry a DECT phone or a deskphone for travel, I’d highly recommend this. I don’t see any other WiFi phone as cheap as this but still provide comparable voice quality. Cheers.The phone is a bit overpriced for the build quality, but the feature-set provides good value. The standard codecs are included, it supports wifi including cert-based authentication and encryption, color screen and instant messaging, pager capability and button mapping, and Bluetooth and speakerphone. Why I dropped a star for this product is because it doesn't support OpenVPN multifactor, or OpenVPN with cert authentication, which for my use case, limits my ability to use this phone remotely. This, it will remain a desktop phone until they release a patch.This does work with Vertical Wave.. just update the WP820 firmware to the latest version from Grandstream's site, then in the phone config, be sure to DISABLE "Support SIP Instance ID" and it will work as expected. If you leave this enabled, the phone will lose its registration with Wave within a few seconds of receiving an inbound call.Also if you aren't using any video features, go through the phone's setting and disable the video calling settings, otherwise it will prompt you each time you place a call if you want the call to be an audio call or a video call.Overall a good value Wi-Fi SIP phone.After a few months with 3 of these phones we are changing our review to one star. I can be at my desk using the phone and in the middle of the call it will drop wifi and drop the call. When wifi reconnects it will be on a different AP. The strange thing is that I can adjust the dB before the phone searches for a stronger signal in setting but it doesn't seem to work correctly. For example I can have the setting at -80dB, have the phone stationary with a signal of -50dB and suddenly it will drop and switch APs, which will drop the call as it takes about 5 seconds for the phone to reconnect. We are on the latest phone firmware of 1.0.7.30 and have looked through ad followed suggestions on the wifi roaming addendum on Grandsteam's website in our investigations. Our APs are Ubiquiti, BTWSo it's a inexpensive voip wifi phone. The setup has a really, really nice GUI interface. If you have used other Grandstream products you will immediately realize that they didn't design the GUI in-house (which is a very, very good thing). On one phone we had audio problems, which can be hard to track down. The phone has some built in diagnostic features, including an audio loopback. By using it we quickly realized it was a hardware issue with the mic and swapped for a new phone on Amazon. Also, the belt loop thing is a joke. The phone is tall and when you sit down it will hit the chair and pop out of the holster. Overall there isn't much available for wifi voip phones at a normal price point....Purchased 2 phones September 2019. Configured by Carolina Business Phones, North Charleston SC. Both phones pre-configured by carrier. One phone had to be returned because charging wire DOA. Phone worked perfectly. Return process was swift. I then purchased two more phones. I use them at home with a detached office. Push button "walkie talkie" feature is a blessing. Love the clarity and volume. Android OS on phone and color screen. Long press on a key pops up a menu for special keys like *&^%$#@ handy for Wi-Fi passwords. This is an excellent phone but make sure your phone service can support the phone as it is new technology.I have purchased a few of these recently, the phone itself works well. Performance on hosted VOIP platform over WiFi is great and it roams between AP's without drops.Why does it keep getting delivered with EU chargers though? The last 2 have both come with the incorrect charger and all Amazon seem to be able to do is to refund it... I want to buy it from you because I want the phone, pack the correct charger.the 150-hour standby time is never achieved, tested two of the same phone and without any talk the actual standby time is between 24 to 48hrs max.The manufacturer need to confirm this as is this a battery issue or over statement of 150-hour standby time?Habe mit dem Telefon meine zwei DECT Sender abgelöst, da die WLAN-Abdeckung mindestens genausogut ist.Folgende Erkenntnis: Es gibt bei mir im WLAN einen fast toten Spot, bei dem das Roaming schlecht funktioniert. Bedeutet, dass das Telefon piepst und einen hohen Packet Loss reklamiert, wenn man sich schnell durch die Zone bewegt. Die Verbindung bleibt erhalten.Was unterirdisch ist - zuvor hatte ich einen gigaset n510 ip pro - ist die Konfiguration. Hier muss man zwingend vom Fach sein, sonst versteht man nichts.Router: OPNsenseWLAN: UnifiDieses Telefon ist mein erstes SIP Telefon. Ich wollte eine "Funkfrequenz" im Haus los werden und DECT an der Fritz!Box abschalten. Mit diesem Telefon ist das problemlos möglich. Die Konfiguration ist eigentlich simpel und im Netz gibt es genug How-To's dazu. Bei mir musste die Fritz!Box einmal neu gestartet werden. Hätte ich das nach dem Einrichten gleich getan, hätte ich mir erheblich Zeit gespart. Seither läuft das Telefon problemlos. Auch das Wechseln zwischen unterschiedlichen WLAN Access Points beim Wandern durch die Wohnung klappt und das Telefonat bleibt erhalten.... zumindestens dachte ich das. Bis dann dieses SIP Telefon in meine Hände geriet. Schon mal ein Telefon gehabt, an dem Ihr KEINE ANRUFE entgegennehmen konntet? Nein? Ich auch nicht. Aber dem Grandstream WP820 ist dieses Kunststück hartnäckig und nachhaltig geglückt.Das Teil klingelt, und wenn ich abnehme, passiert.... NICHTS!! Es klingelt einfach weiter und keine Verbindung kommt zustande. Ich habe schon viele SIP Telefone erfolgreich konfiguriert und betrieben (u. a. auch andere Grandstream Modelle und mehrere SIP Softphones). Aber so etwas ist mir noch nie passiert. Trotzdem habe ich zunächst mal versucht, in der (abstrus komplexen und überladenen) Systemkonfiguration des Webinterfaces des WP820 nach dem Fehler zu suchen. Vergeblich. Dann habe ich den Grandstream Support kontaktiert, was wiederum ein etwas nervenzermürbendes Erlebnis war. Ich habe über 4 Tage hinweg zuerst mal Fragen beantworten müssen (die teilweise schon längst beantwortet waren und deren Relevanz für die Problemlösung mir - sagen wir - schleiherhaft waren.).Zuletzt wurde ich dann aufgefordert, einige Konfigurationsfiles downzuloaden und an den Support zu schicken. Mit dem Ergebnis: "Es liegt nicht am Telefon, sondern an Deinem SIP-Provider".Einfach lächerlich diese Aussage in Anbetracht dessen, dass ich aktuell gerade 6 SIP-Phones und 2 Softphones bei eben diesem Provider erfolgreich betreibe.Mein Fazit: Dieses Modell ist ein ganz großes Armutszeugnis für den Hersteller.Musste es daher leider zurückschicken.