Man, other than Flatout, I consider all those to be A+ titles. Good choices. (Has Ninja Gaiden envy...)
Flatout is fun as hell man. The racing isn't the best, but the various mini-games are a blast. High jump and bowling are my personal favorites. Right now though, Orange Box and Uncharted are really eating up most of my time.
I have to agree with Mr. Moore there; Flatout's mini-games are fun as hell, I love the High-jump and bowling ones. They really are good fun, if a little tricky! Also, hooray for XBL Freebie. The game looks pretty cool, though for 800 points, I'd have prefered the Halo Heroic map pack.
I think by now everyone who would be getting Heroic would have gotten it already (thereby pissing off lots of people who already bought it) and it'll be free in a couple of months anyway. As far as Undertow goes, I wasn't very impressed with it, but I cant argue with the price.