Yep mine is doing that...do a search on choppy...sluggish. There are plenty of threads. Apparently it occurs on machines equipped either with Intel GMA 950 or Nvidia video cards.
Count me in on Choppy window dragging. Almost seems like it hiccups and skips a few times as if the VSnyc isn't working 100% of the time... another word for that would be BeamSync (such as Apple calls it in Quartz Debug)