The most commonly reported problem with the Release Candidate is a bug that causes crashes in IntelliSense when used on a multitouch capable system. We’ve released a patch for the RC to address this issue. You can download it here: http://connect.microsoft.com/VisualStudio/Downloads/DownloadDetails.aspx?DownloadID=26662
If you find anything else broken, please report them on Connect. We’re still fixing any serious issues that are found.