I upgraded to an SSD while on Leopard, and was amazed at the speed. Snow Leopard continued to impress. Lion slowed things down terribly (even with the SSD!), but I have good news: ever since Mountain Lion DP2, it's been fast again.
Given that Apple has fixed none of my reported bugs in 10.7, but I can't reproduce many of them in 10.8, I wonder if it even makes sense to analyze 10.7 anymore - seems it's a done deal for Apple.
