Well, I have just upgraded my Mac from Leopard and personally I am loving it! Instead of writing 'another' lengthy review of how i found the installation and the end result, I thought I'd link to a great user review I read earlier today!
This review literally sums up all the points I have to make! Thanks to @Burnspot for taking the time to post this. Whether you have just brought Snow Leopard and want to know what the new features are, or you are wondering if it's worth the effort / money to upgrade, this review will help you!
As a side note I intend to post some of my own thoughts after a few weeks of usage!