InternetTabletTalk runs a compilation of user reviews.
Got mine yesterday. Haven’t tested wifi yet as my wifi modem is currently being delivered, but played about with the video player.
The built-in video player tries too hard to display a perfect image. With a 25fps 352×288 MPEG, it drops frames, but gives a crystal-clear image. I’d have forgiven it if it produced a few artifacts but maintained the framerate.
DivX’s aren’t any better - right now I have to encode them to 352×288 @ 15fps in order to get something that would play. It plays flawlessly though, which implies that the image quality/framerate balance is tilted too far over to image quality.
But hopefully there are/will be other media players out there which can handle DivXs that are 702×576 @ 25fps - I’m open to suggestions here.
The display as a whole is fantastic, very bright, very clear, no dead pixels like the PSP has.
Handwriting recognition doesn’t work too well for me, but then again I have untidy handwriting so I’m going to have to adapt.
The User Guide is lacking where it comes to the RS-MMC card usage - it doesn’t tell you that you have to remove half of it before inserting it. I thought the card wasn’t going all the way into the slot, and it wasn’t until I measured the depth of the slot that I realised that half of the card is meant to slide off.
The built-in speaker is very loud and clear, which surprised me.
Charging was very quick, and it’s great that you can use the 770 whilst it’s charging.
The plastic stand that comes with it is cheap and nasty, but is at the right angle for desktop use, but I want a sharper angle so I can rest it on my chest whilst watching a movie in bed.
That’s my review after six hours usage - tonight I sort out wifi 
Wifi works nicely with my PC using a shared Internet connection over WLAN ad hoc network. Pages open nicely on the browser. Speed and rendering are as good as one can hope.
Got my 770 today and I was genuinely surprised. I have seen all the previous Nokia multimedia devices based on Symbian OS. N770 on linux really kicks the ass of the communicator lineup when it comes to browsing.
The UI is conventional and easy to use. No nonsense buttons scattered on the device.
Video and audio works nicely, considering that the 770 is not optimised just for this kind of use. I guess a bigger memory card has to be aquired.