While I agree there's an anti-incumbency theme to all of this, the Dems are going to face the brunt of this much more than the GOP due to the nature, and execution, of the healthcare bill. Old school (god, war, and pork) GOP candidates will be vulnerable, but I think incumbent fiscal conservatives will do very, very well.
Once again we are where we are at before the 2004 campaign a 50/50 nation and the map may very well play out in a very similar fashion as it did in 2004 with a few exceptions.
Personally, I'm expecting the news to be worse for the Dems in 2010 than it was in 2004. You can see that in the numbers in CA, IL, PA and from the recent results in NJ, MA, and VA, all of which are substantially to the right of 2004.
It may cool down between now and November, but it looks ugly for the Dems today.