Just wanted to point out that Push2 isn't made by Akai anymore, it's all Ableton at this point. So the pads are totally new and redesigned on the new unit. They're a bit softer and have more of a matte finish that makes them easier to play. Consistancy across pads is MUCH better (and the overall sensitivity is a lot more configurable), and color variations pad to pad (rainbow push) are gone.
The new Push 2 is a tiny bit lighter, and a tiny bit bigger on the sides (same height). The buttons are now recessed and have a more positive click when you press them, and the labels on the buttons are much easier to read now. Also, the top plate is aluminum now, so no more peeling black rubber on the corners.
Obviously the display is great, especially the viewing angle and how well they implement the colors of the display with the colors of the pads and buttons. No more need for SeaPush hacks, now the pads reflect the track color in a lot of areas on the controller. Being able to graphically edit samples in Simpler right from controller is great.
I'm happy to answer any questions I can about it, though it might take me a couple hours to reply as I need to catch up on some much needed sleep after a LONG weekend