We have the Hiptop/Sidekick 3 at T-Mobile... it is better than the SK2, but there are still some not-so-great things, like even though it has an MP3 player, you can't set the mp3's as ringtones... you still have to buy your ringtones from the catalog :-/
I say go for the HTC Wizard, which I think SunCom now offers... it is based on Windows Mobile, and at least here (T-Mobile) it is the same price as the SK3...