GNex has zero shutter lag. This is, I think, the first cell phone camera to boast of such a feat. That I've seen, anyway.
I'd take that over the piddly 3 megapixel difference compared to SGS2. HD video recording appears to be same quality, as well.
Though, for what it's worth--I'm extremely happy with my SGS2 and feel no qualms with the GNex coming out soon. I thought the 4.3" size of the SGS2 was perfect at first (mine is international), but now I think it's either slightly too big, or at the very most, the largest size I could possibly want in a phone.
For the OP: I purchased mine--international unlocked off of Amazon. Paid right at $600, but applied that to new Chase Freedom card dela that gave me instant $250 cash back with first purcahse. that has since been credited, so I was in the end able to purchase an unlocked SGS2 for $350. Those deals for the cc are quite ubiquitous these days, btw.
My TMo contract had expired, so I wanted to go for a serious upgrade without having to sign any new contracts. I'm currently still using my TMo SIM card with new cheap plan (Still no data, lol). The problem is that the international version, if using TMo, locks you to Edge (the weird bands that TMo uses). That doesn't appear to be a problem for you, so...whatever.
Another option is to look into WalMart's Straight Talk service plans, which are extremely cheap "unlimited," and use ATT's network--which means the international SGS2 could be fully utilized on the ATT Network with a very cheap monthly plan, and no ATT hassle. (You have to buy the proper phone--$100 up front on top of monthly contract--to get this to work)
From a few benchmarks floating around, and including Anand's preliminary benchmark (they mention the full review will be out soon), the TMo SGS2 somewhat significantly outclasses the "real" SGS2 with Exynos in browser and other benchmarks. It even matches or beats iPhone 4S. However, it will likely be destroyed in games compared to the Exynos Mali, or so we expect. It's also the larger screen at 4.5" instead of 4.3'
Though, this idea that Sam's Club has one on ATT contract for 0.99 on BF--this sounds like a no-brainer to me. That is a serious phone for free, that should remain in the top tier of phones for another year or so. It is also, probably, the US version that you want--though it would be locked to ATT.