The IU is generally smoother, there's a nifty screen-off animation, over-scroll glow to let you know you've reached the limit of what you're scrolling through, front facing camera is said to be active in video calls, um... if anyone would care to add anything else I'm drawing a blank on the rest.

You can keep your EXT4 conversion from gummy Froyo if you want to flash gummy Gingerbread. There's an instructional thread at XDA.

 

I flashed Ep1w last night with the ext4 kernel and this thing is fast. I'm getting near 1800's in quadrant. Battery life is pretty good too, been off the charger for 18 hours now and at 20% with light/medium use.