Neowin has an article up detailing some of the changes going into the RC of Windows 7 that have been made since the beta was released. This is just a small sampling, but Microsoft emphasized this was a result of user feedback during the beta process.
In the first few weeks of the Windows 7 beta we had over one million people install and use Windows 7. That's an astounding number for any beta test and while we know it has been fun for many folks, it has been a lot of work for us--but work that helps to raise the quality of Windows 7. When you use the beta you are automatically enrolled in our Customer Experience Improvement Program (anonymous feedback and telemetry, which is voluntary and opt-in in the RTM release). Just by using Windows 7 as a beta tester you are helping to improve the product--you are providing feedback that we are acting on in a systematic manner.
Head over to Neowin to see more details of some of the changes in Windows 7.
Link: Windows 7: Changes since beta for the RC