Nvidia put out a geforce update yesterday and it gave like a 60% performance game with Skyrim specifically, and they named some other enhancements. It just depends on the update and the game, but yes they can help.
And to add to cody's reply. Some games may recommend or require a driver update. also if your running SLI/Crossfire, the drivers for Multi GPU profiles may be needed for that game. But yes to answer question. I update my driver to the latest one when its released. if its not doing what i want, or it has issues. I roll back to the driver before it
The latest driver package for your card will support all GeForce 8 and newer cards installed in your system with a single installation. This is generally true of all families of hardware that share the same drivers.