I've had but a single issue with X2:
When dragging a drum loop into a track (via the Browser) and hitting play... I lost control over the transport. Couldn't do anything to stop it... (had to shut down the Sonarpdr.exe)
Haven't been able to reproduce the behavior...
Otherwise, X2 has been great.
Love all the small improvements to workflow.
X2 kinda reminds me of Win7 after Vista
Vista was pretty solid after SP2. Win7 was a nice refinement on Vista SP2.