No we didn’t miss versions, this is the first release after 5.0.51b. This is a bug and security fix release and it is available in source and packaged format for Mac OS X. Because this is a security fix I would urge you all to upgrade your MySQL server installation.
Check all the fixes that are listed on the release notes to what issues are resolved.
I’ve compiled this version and did some simple tests on Leopard and Tiger and both can be compiled and installed using the instructions in the documentation set without problems.