To me the main gain is that I don't need to remember how certain language does certain things. I can center a div without having to worry about which browsers support which instructions, etc.
It's quite freeing.. for the past 4 months I have been mostly focusing on spec development and just reviewing the implementation. Then I can leave say 6 sessions coding in parallel while I refine the next spec.
Of course, the more backend the better,.since AIs can't really test interfaces well yet.
