Well, I know this isn't an iPad2 or Atomic discussion specifically, yet I wanted to say how pleased I am with this browser now that it has more RAM available (512mb in the new device).
On my 1st-gen model (with 4.3) I couldn't open more than 5 or 6 tabs without getting low-memory warnings or having it quit.
With the ipad2, Atomic hasn't crashed one. This is significant to me as one of my primary uses of this device is accessing the web. That experience has become a lot smoother.
So while there are many nice reasons to like the new iPad: faster hardware, thinner/lighter, cameras, etc. I think the importance of the increased RAM is often overlooked.