Upgrading 2008 R2 servers to SP1

A while back there were some issues with 2008 R2 and SP1 installations (as seen here).

Sometime has passed, so is it safe to upgrade the servers to SP1 or it's still not a valid operation at the moment?

Best regards,

We have successfully been able to upgrade to SP1.

Just consider Acacio's post first should you get any issues :

It should be good to upgrade.

I have 2 servers with Windows Server 2008 R2 SP1 running (one of them since August 2011) and I never had any sort of problems with SP1.