The general rule of thumb for graphic card display drivers is "if it ain't broken, don't fix it". When NVIDIA releases a new product, over time software developers learn more about the architecture, and are able to gain better performance from this architecture through updated drivers. As a product matures, driver updates primarily provide bug fixes and compatibility with newer software.
If your NVIDIA based graphics card is a newer model, it is recommended that you update your graphic card drivers regularly to get the best performance and experience from your PC. If your NVIDIA based graphics card is an older model, then we suggest you update your drivers only if you are experiencing problems while running newer software on your PC.
For the complete list of changes, please view the Release Notes available from the NVIDIA driver downloads page.
http://www.nvidia.com/Download/index.aspx?lang=en-us