I use my cards mostly for Distributed Computing projects. With every successive driver update since the 400 series of drivers have come out the times to complete work units has increased by about a third. NVidia is severely crippling the OpenCL on the older cards with their new drivers. You probably won't notice it on games, but when you are running it at 100% over long periods of time doing discrete compute, it is there.
Tell me that isn't done by design, so people will go out and buy the new cards. Of course it is, it is the American way now. Look a what Apple has admitted to doing to their iPhones (over load them with an operating system that wears out the battery faster, making people want to get the newer, faster ones). NVidia is doing the same with their drivers. In an essence they are no longer supporting the older cards that will run any game on the market as well as a new card at half the price.