Unique to the T3, of course is the screen.  I love being able to place it in landscape mode for use with spreadsheets, etc.  And that brings me to Docs To Go, not a T3 only application but IMO much more practical with the larger screen.  As far as not having a keyboard, Palm now has virtual graffiti which allows you to write anywhere on the screen and have the OS recognize the characters.  In fact, having a keyboard would not work well in landscape mode.  The T3 also needs nothing additional to play MPs, other than an expansion card.  And it has voice memo capabilities.
I don't use Bluetooth, possibly I'll consider a Bluetooth cell phone the next time I upgrade.  There is supposedly an expansion card that will be out this year that will support Wi-Fi, I hope so.  My house has Wi-Fi and I would love to be able to check email without firing up a PC.
Here's a good review:
http://www.brighthand.com/article/Ha...n_T3?site=Palm
And while you're at that site, check out its forums:
http://discussion.brighthand.com/palmhandhelds/