If the performance degradation is considered a bug, that changes the picture a little bit. But I agree with nirvdrum's comment on using exceptions as control stuctures.
Its easy enough to spout platitudes like "don't use exceptions for flow control", except remember two basic facts about the commit that I linked:
1. It was using exceptions for flow control as an optimization 2. That optimization was indeed faster on 1.9.2
On top of that, when the rails team was notified about how bad this "optimization" was in 1.8.7, they immediately fixed it.
I just don't see how any of this fits into "don't give a shit about performance".
I think it is very interesting that the specific test produced in the original post is actually faster under Rails 3 and Ruby 1.9.2 than it is under Rails 2 and 1.8.7.
My only grief with you, fauigerzigerk, is that you claim the Rails team doesn't "give a shit about performance", when the performance problems seem to be related to people using an older version of Ruby. I think you are making an extraordinary claim -- that the rails team doesn't "give a shit", in in fact, they clear do give a shit.