Microsoft has released SQL Server 2008 R2 Service Pack 1 Cumulative Update 10, which is Build 10.50.2868. I count 15 fixes in the public fix list. Some of these fixes look fairly important, so you should take a look at the fix list.
This Cumulative Update is only for SQL Server 2008 R2 Service Pack 1. It will not work with any other major version of SQL Server or with any other Service Pack Level. Speaking of SP levels, I think you should be planning on moving to SQL Server 2008 R2 SP2 if you have not already done so, since SQL Server 2008 R2 SP1 is due to be retired in about six months.
When a SQL Server Service Pack is “retired” that means that it is considered an “unsupported service pack” by Microsoft CSS. This means that you will only get limited troubleshooting support until you upgrade to a supported Service Pack. It also means that there will be no more Cumulative Updates for that Service Pack.