Enemy Territory: Quake Wars
Decent frame-rates from all cards in Enemy Territory: Quake Wars, and that's with options cranked to maximum.
Again, near-identical performance from the two overclocked GeForce GTX 260 cards; both are around 13 per cent faster than a stock-clocked model and, again, obviously, slower than a GTX 280.
We'd feel very comfortable playing the game at a 24in LCD-friendly 1,920x1,200 setting on all cards, though.