FWIW, I had both X1 and X2 on my machines the day that both were available.
X1 always ran well for me.
As I've mentioned before, I tend to use Sonar in a very traditional tracking/editing/mixing vein (no loops/matrix/Vvocal and I generally use 3rd party EFX). I think that's part of why I didn't experience major issues.
Another thing I noticed is that X1 seemed to be more prone to issues when running on "older" hardware and especially when running under WinXP.
Never had the issue with Pro Channel turning on/off... or any other show-stoppers.
The most common issue I had was the FX Teleport error when exiting Sonar.
It's an outstanding bug... but it doesn't affect anything (project already saved and unaltered) so it's but a slight annoyance.
On my DAWs, X2 runs just as well as X1. There are some nice overall improvements/refinements.
If you look at other options, you'll see reports of issues with Cubase 7, Studio One Pro v2.5, Digital Performer 8, etc. The grass always seems greener...