Ludwig
I have X1 and X2 installed on my system - win 7 64 bit, Intel i7 2600k @ 4.5GHz and 8 gb ram.
I installed X2 and used it for a couple of days, found it unstable (in my case mainly very strange graphics bugs) so went back to X1.
X1 is running as it did before install of X2 and is very stable.
The only thing MIGHT be (and I do say might as I think I may be being just slightly more paranoid than usual!!!) is there may have been the odd minor graphical hic up (jumpy console screen sort of thing) but I REALLY do mean minor.
To be honest I don't think if I were you I would bother with X2 just yet - I am busy at the moment and I could probably have done without the distraction of a few days wasted trying to get used to the new features - personally X2 is "retired" for me until first patch, which will hopefully sort out the weird behavior.
Nigel