I don't know that I'm the best person to review this, but it looks good to me aside from the other comment I made. I tested a few applications, and if CrystalMark is to be believed, it improves GDI performance.
Thanks, this is really appreciated. I think that if someone shows enough interest to look at the code and make comments, their advice is worth considering as a review. But then if you don't feel like it, feel free to remove yourself.