I have used HTC P3600 since January 2007. This is my second smartphone. And it was my third PDA since 2003.I purchased this smartphone for the GSM quad band capabilities. There have been no problems at all. I have used it in Africa and Europe. I have used local (African and European) SIM cards without any problem. I have used it on T-Mobile network in the US, Africa, and Europe. Also, I have tested it on the AT&T; network here, too. Just replace the SIM and make a call!What makes this smartphone worth the price? WiFi, 3G, and two cameras (front and back) with video are top shelf features. Plus it has all the other must have stuff: touch screen, blue tooth and miniSD.It is a feature-rich and fully functional smartphone, that is, PDA with a phone. The PDA operates on Windows Mobile 5. There have been no compatibility issues with running third party programs. A noted improvement over previous PDAs. I have never had to do a hard-reset. The number of soft-resets are about same as with my other PDA (IPAQ 3600 and Samsung PPC6700). I think it is just PDA thing when you running multiple software programs with PDA processors (400Hz +) and PDA ROM (128 Mb +).The phone is straight forward and functions very well. I have not experience the video conferencing capability because the US carrier are just rolling out their 3G networks.More internal memory and a faster processor would make this a super smartphone. Also, a slide out keyboard would be handy.