We've had the Sidekick II for about two months.  Although my 11-year-old likes it for its buttons and Gee Whiz value, I find it very awkward to use as a phone.  It doesn't have a normal keyboard, so you must flip the screen up to press the keys, then flip the screen back down to listen and talk.  When you get into a voicemail situation, you have to keep flipping the screen up to "press 1 for English", etc.  Very annoying.