Most of these have already been previously mentioned but...
-Higher resolution, larger display
-Improved screen touch response (according to reviews... we'll have to see)
-Larger, offset key keyboard that is one of the best on a phone (again, according to reviews)
-Official TF3D2 so it should (hopefully) be more stable than the current VGA ports for the TP1
--Includes landscape TF3D, much better calendar, TF3D screen customizations, more settings, etc.
-Better speakerphone and noise cancellation than the TP1
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TBD but it looks like the CDMA version of this phone will have a 3.5 audio jack
-Better performance than TP1, xperia X1, omia i900 (but not as good as the new omnia II)
Downsides...
-No flash
-A lot of things to be determined yet... the biggest is real world performance, batter life, overheating, etc.