I thought I'd give X2a a go this week after being very disappointed in the stability of X2.
I too have been seeing a 'ripple' or 'shudder' effect in the graphics after maximising then minimising a track, and my audio drops out when adjusting EQ bands on the ProChannel. I can adjust the Sonitus EQ till the cows come home without any issues to speak of, so I suspect there's something screwy going on with the ProChannel graphics. We're not talking big projects loaded with soft synths and plugins either. My PC is only 6 months old, 16GB RAM, i5 processor, dedicated graphics, Win7 with latest service packs, latest video drivers etc.
X1d runs a lot smoother and 8.5 is golden. X2 and X2a are stinkers (for me) though. I'm not about to change my PC to make X2 run - auditioning other DAW's seems like a better route at this point.