https://github.com/rails/rails/commit/86acbf1cc050c8fa8c74a1...
For our application that meant bringing 1 of 3 application servers down and slowing things down in general. So we're stuck with 3.0.5.
From what I understand the Rails community has declared 1.8.x as a thing of the past (tbf it IS a thing of the past. But in a non-perfect world migrations our not always easy). This may be a good thing (it forced us to march towards 1.9.2) but I'm sure it has caused a lot of problems.