As of yesterday we have decided to release RC0 as a public download.Everyone start firing up your virtual machines or test servers because here it is! Please make sure you check the "What's New" section in the Books Online.
Play around with it, test it, break it if you can and give your feedback. Connect is the place to be if you have any suggestions or issues, if you do so you will make the RTM version of SQL Server 2008 an even better one!
Are you still reading this? I hope you started the download before you read the rest of this post ;-)
BTW. Do not forget the RC0 feature pack which contains - among many other things - the Data Mining add-in for Excel.