Well, topics name says for itself 
Not so long ago (yesterday) I ran GSB under my new Windows 7 x64 bit Professional (nVidia GTX 560 Ti, driver 290.36) and encountered a lot of them:
While holding and placing ships (after being placed they are smooth/have AA):
Under XP they are smooth if I remember correctly:
Always jumps between not very smooth and smooth if zoomed out:
Always jumps between smooth and not smooth (Smooth always, only if mouse over. This unknown line exist sometimes):
Present in both, Fullscreen in Windowed modes!
Under XP they re-sized smoothly if I remember correctly:
