Do you need to upgrade? If everything you are currently playing works fine and maxed at whatever resolution you play I don't see the need to upgrade since you still have a nice card. Of course if you just want to upgrade cause its fun then by all means check out some benchmarks like JMMD pointed out. It's definitely a better card and the best bang for the buck atm imo. Not sure where you live but you can even get the GTX 460 for $200 here in the US.
What red said.
Also, if you're planning on spending $250 on a GTX 460, you will be looking at a heavily overclocked version (Palit Sonic Platinum 800MHz core for example which will increase performance over stock (675MHz) by about 20%.
TPU's review of the MSI Cyclone that is clocked midway (725MHz) between stock and the Palit card will give you an idea of the increases available from factory OC'ed cards (the review includes the GTX 280 for comparison)