My wife has the 8100 and is on her second phone after they replaced it due to fluctuating volume during calls. The new one is doing the same thing and is a common complaint. The camera sucks, both handsets had a huge delay between pushing the button and the picture actually being taken. Voice activated features are much better, and easier to use on the 815 (I got the 815 after she had problems). The speaker phone on the 815 is great! The 815 is not as pretty, but just plain works better in almost all respects. The 8100 is probably a better MP3 player due to the external controls, and is more adjustable. There seems to be more options you can change: reminder intervals, pics on the screens are independant, movies as wallpaper etc. And the 8100 is well built; solid. But it just doesnt work as well. My wife is stuck, her loss was my gain