Yes, I've experienced it too.
Definitely not as stable and solid as Cakewalk/Sonar... some on this forum recommend using a different DAW for MIDI heavy projects, but I'm hoping the next release fixes it.
My issue is with Toontrack's Superior Drummer. Even the audio previously recorded (and solid) seems to "float" timing- wise after SD3 was added to the project.
...and to get the notes to sound in time, it's like they need to be pushed ahead of the beat, to compensate for the VSTi latency...so forget quantizing...
Yes - this one needs to be addressed, for certain.