SQL Server 2008 R2 is released and have been a stable product since the day it is released. I have not received any complains or rants from any of my customers who has upgraded to this version. The number one request is how one can learn about the new features of SQL Server or how one can get going in using SQL Server 2008. Microsoft has released SQL Server 2008 R2 Developers Training Kit. This is awesome kit and I just suggest to have a look at the content one time.
Here is what MS say for this kit:
SQL Server 2008 R2 offers an impressive array of capabilities for developers that build upon key innovations introduced in SQL Server 2008. The SQL Server 2008 R2 Update for Developers Training Kit is ideal for developers who want to understand how to take advantage of the key improvements introduced in SQL Server 2008 and SQL Server 2008 R2 in their applications, as well as for developers who are new to SQL Server. The training kit is brought to you by Microsoft Developer and Platform Evangelism.
I suggest that you look at the content and use this free kit to upgrade yourself to SQL Server 2008 R2.
Reference: Pinal Dave (http://blog.SQLAuthority.com)