If you need to test the new RemoteFX or Dynamic Memory features in W2K8R2 RDS or Hyper-V respectively, then you can download the beta of the upcoming first service pack for Windows Server 2008 R2 (and Windows 7 for the client-side bits) here.

I wouldn’t bother installing the beta service pack on a Windows 7 client unless it’s going to use these features or you need to do application compatibility testing, a service pack is generally a collection of fixes and rarely new features or serious performance improvements.

If you do install the beta service pack on a production machine, make sure you have a backup or are prepared to reinstall it, just in case ;)