No we didn’t miss a few versions, this is the first new release after 5.0.45. By the way this is a bug fix release and it is in source format only. This means that you definitely need to compile your version if you are affected by the bugs that are fixed. If you don’t have any problems or concerns don’t upgrade.
Check the bug fixes that are listed on the release notes and check if you are affected in any way.
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.