Stuart Rothenberg is a well respected analyst and far from a conservative hack and he says that House is probably not in play in 2012. He bases this on a review of redistricting changes that he says probably give the GOP a slight edge.
I tend to agree with his review although I certainly can see where people could dispute one part or another. Also worth remembering is that in many cases where the GOP has controlled the process they have not so much moved to give themselves more seats but to solidify the ones they have (the advantage of being in the majority is all you have to do is staus quo).