For all who are using to a 5.1.x version. This is a bug fix release and it is up to you if you want to upgrade. Check all the fixes and changes that are listed on the release notes to see what issues are resolved and if you are affected. Most of them are about replication and partitioning, none of which we actually use in our setup.
I’ve compiled this version and did some simple tests on my test servers and it worked without any problems.
Read the documentation on how to ugrade MySQL.