If someone games at 1680x1050, then there is no point in getting a GTX, 4fps faster in crysis is hardly worth £70, the only reason to choose a GTX over a GT is when you are gaming at a res higher than 1680x1050, and I'm not saying this because I have an 8800GT or anything like that, its just what I see in benchmarks, most of the benchmarks, if not all suggest that the GTX is not worth an extra £70 over a GT at 1680x1050 as the frame rate increase is minimal and really you're not going to lag in anything at 1680x1050 apart form crysis, in Windows XP at 1680x1060, shadows medium, then I use a cfg which effectivly give you very high quality of better for the performance of high quality, and its smooth enough all over right up untill the big ship deck, it does get choppy abit in the snow areas, but a GTX does too.
Now if you can get GTX's right now for £200, then I would deffenitly go with a GTX over a GT, as long as the 8800GTS was not coming out anytime soon, the best option is to wait for the GTS, not long now, its going to be cheaper than the GTX, push GTX resale value down even more, and its possible it could outperform the GTX, but we need to see some propor reviews untill we can say for sure.