Some of the improvements to my workflow that I like are the track view zoom, auto track zoom, take lanes, automation lanes and improvements in PRV. These were worth moving to X2 alone.
The audio engine appears less glitchy.
Breverb and Console Emulation are EXCELLENT (if you're on Producer). RMix might be cool, too, but not really had time to study it yet.
I really like the improvements, many of them subtle but add up to A LOT. I have only mentioned the ones that came to mind. There are many others.
I loved X1, and am loving X2 even more now. X1d was rock solid for me, and X2 is looking that way since quick fix (and now X2a).
As FBB said, you can always go back to X1 (as it's not worth uninstalling it) if you're not happy, and as you've already paid for it you have nothing to loose. Make sure you install patch a.
Let us know what you decide, and what you think of X2.