Wow, now's one of those rare times when I wish I could double-vote on a node.

I'd say that optimization should be really, really rare. Correctness is *so* much more important that it really should get almost exclusive attention. If for example, you have a really horrifically borked query due to bad DB indexes, I'd suggest that you're facing brokenness not optimization at that point.

Think *very* carefully before trading simplicity for performance.