I agree with Boehner. A 67% chance of a GOP House sounds about right to me.
Until some evidence of a wave starts presenting itself, this prediction is merely to remind incumbents to not get lazy, and in general, we should see warnings of a wave by now if one were to occur.
Romney's performance is much less important than people think vis-a-vis the House. Senate is a different story.
I definitely agree with the bolded part and I'm inclined to agree that Romney's performance is much more important for Senatorial elections than House elections, generally speaking. However, I'd argue that we might not see as many warning signs in general if it were a "bipartisan," anti-incumbent wave (Note: I'm not saying that such a wave is going to occur in 2012, just that if it were to occur, it might not be clear yet).