I currently use an Nvidia GTX 295 and play mostly FP shooters (MW2, Mass Effect 2, Fallout New Vegas) role playing (Oblivion) and strategy (Shogun Total War, Civ V).
Although I don't have a 'problem' playing the above, with MW3, Skyrim and ME3 due out soon, I am curious as to whether or not moving to something like a GTX 580 with its DX11 capabilities might be worth while. My existing card will exceed the minimum specs on the new games, so I expect them to play, even to a reasonable level of graphics with decent frame rates. But I always wonder if I'll be missing out on a better, more realistic experience and whether or not a new card will get me there.
My rig has an i7 920 CPU running Windows 7 Ultimate 64bit on an ASUS Rampage II Extreme mobo with 6GB RAM.
Another path to follow might be to await the next gen cards (GTX 600 family???), but who knows ahen they'll be available.
I dont think you are missing anything too important without dx11, especially so close to the next gen cards, I would wait. The move from 40 to 28nm should give nice boost on perf/watt over current offerings.
Rumours still has it that amd might get something out by the end of the year, nvidia sometimes in q1.
I used Wikipedia as my primary decision research tool toward what video card to get since my GeForce 7600 GT is 7 generations behind (and now, about to become 8). Then again, I don't do any gaming on my computer outside console games on a TV tuner.