Last night Microsoft has released Cumulative Update #2 for SQL Server 2008 R2 Service Pack 1. The build # is 10.50.2772 and it contains 14 fixes, a few of which are wrong-results bugs or cases of access violations.
You can download the update here:
It was also mentioned on the SQL Server Release Services blog. It seems to be implied that some of these fixes were included in CUs 7 or 8 for RTM but were left out of SP1 and SP1 CU1, but I haven't validated that by performing a diff.
My necessary disclaimer these days: This update is NOT for SQL Server 2008, and it is NOT for SQL Server 2008 R2 RTM.