I have the w810i and previously had the K750i. Both phones are excellent, especially the camera which is 2mp for these models. The K800i looks like an upgraded k750i with the cybershot designation and 3.2mp capability. Keep in mind though, that these camers use a cmos based camera and despite its high resolution, cannot compare to the quality of real CCD digital technology. Expect artifacts and noise.
I was going to get this phone, but the 600 dollar price tag was a bit steep for me. The media player is excellent for music and not bad for 3gp or mp4 video and that phone should have the Java v7.0 software which means better 3d/2d performance on a number of games. I can post example pictures of what the w810i camera can do, and just imagine a higher resolution for the k800i.
Also keep in mind that internet access on an international phone not offered by your service provider will = some headaches. Cingular support seems rather lacking in getting their w600I software downloaded to my w850I. Atm I'm stuck with the European "E-plus" software for net browsing and email checking. And even if u do get the software, u cant do everything a supported phone can do, like purchase ringtones and games over their net carrier.