I hear what you are saying about exceptions, but you also have to live in reality. Look at danielparks benchmarks in this thread; rails3 under 1.9.2 is faster than rails2 under 1.8.7.

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".