There' s a need for one unified thread on this I think.

Things that are very importatnt :

-No Dual HDMI out in any version of the console
-Blue Ray Drive 2X speed (72Mbit/s)
-up to 4 (not 7) Wireless Controllers (with tilt sensors that don' t even compare to Wii-mote) with GUIDE button similiar to ones on 360 controllers.
-20 GB version like Joe wrote has no:WI-FI,HDMI,Memory Stick and SD cards reader (and could lack other features,)
-Most Games in 720p (probably only upscanned to 1080p)