I've owned my 6600 for a week now. Can't say I'm impressed with it.
Incoming calls don't show caller name, just number (name is in address book)
Regular 'not enough memory' errors for sim updates
Phone turns itself off, and when turning back on, error messages 'App closed main' and 'App closed mce'
iSync (Apple Mac) regulary needs phone to power-cycled to work.