It's still a fairly decent reference if you need to update your software for 1.9...

Locke on Oct 29, 2008 | parent | context | favorite | on: Ruby 1.9.1 preview released

It's still a fairly decent reference if you need to update your software for 1.9. Several incompatibilities I ran into were listed there. For others problems, I did have to search the mailing lists, though.