1) JIT Compiler (2x-5x speed increase)
2) Dedicated phone and browser buttons on the home screens
3) USB Tethering and Wifi Hotspot
4) Flash 10.1 capable (when downloaded from the marketplace)
5) Marketplace upgrade allows comments to be ranked as “helpful, unhelpful, spam”
6) Copy and paste in Gmail
7) Apps 2 SDcard
8 ) Auto upgrades/Multiple upgrades in the marketplace
9) Bluetooth Voice Dialing
10) New camera buttons allowing you to set options quicker
11) Faster down/up speeds over wifi (I’m seeing 3G increases too. Used to get 200-300kb down, now pushing 800-900kb in same exact area)
12) New “Car Home” Layout
13) Google Talk and Messaging are now white background with black text (reversed)
14) Forward and Back buttons in Gmail
15) Calendar App uses small blue dots instead of large green bars in month view.
16) Call log now combines multiple calls to a contact instead of listing each one numerous times.
17) Colored trackball notifications appear possible, but app specific? (link)

I’m sure I’m missing a few things, so feel free to reply.