I've had my 700WX for nearly a year and have few complaints about it. My biggest one has little to do with the phone and more to do w/ Vista and WMDC. The 700WX's greatest asset is it's memory 128MB vs 64 on most other PPC's. There's also no shortage of 3rd party apps that really help customize things. With a little work, you can operate your device one handed.
As for the 700P or 755P, these use the Palm OS, not WM and therefore are not PPC's. Additionally, unlike WM based devices which allow multi tasking, Palm OS devices do not allow this.
Hope this helps your decision.
