Only counting games I bought with NO store credit or freebie online points, I'd say about 8 games. I kind of got suckered by a few of 'em, I'll admit, but I was happy to support the industry. Braid, Castle Crashers, Mirror's Edge, Left4Dead, Fallout 3 and Rock Band 2 come to mind.
Of course, I haven't actually played L4D or ME yet because A) Fallout 3 has dominated game time, and B) my Elite red-ringed...