I'm liking Lion so far, although I installed it late last night and didn't get a whole lot of time to check it out. To me, it's a much bigger deal than Snow Leopard because there are a lot of user-visible changes, and Snow Leopard looked and worked 99% identically to Leopard and mainly ran faster and smoother. Snow Leopard did introduce cool under-the-hood computer science-type innovations that were invisible to users.
But in Lion: I really like the new linear Spaces and Mission Control. I never used Spaces before because I didn't like the feeling of "out of sight, out of mind" with all the apps that were running off-screen--even though I do it at work on Linux. But with Mission control plus the super-easy 3-finger swipe to move between screens, Spaces has, to me, suddenly become a very natural, additional way of managing lots of running apps--especially since I have a laptop which is a small screen.
The new iOS-style behavior of bouncy scrolling endpoints and disappearing scroll bars I also like. Scroll bars are nowadays mostly to tell you what part of the document/page you are looking at, more than actually manipulating to scroll. The two-finger scroll/scrollwheels have taken that function over for a long time now.
Finally, the new process management system where the OS can autosave the state of an app you aren't using and shut it down in the background to free up resources for the apps that you ARE using is kinda mind blowing for me. That's how the mobile OSes work, and it makes sense to maximize your resources for the tasks you are working on. You don't need to be bothered any more by five apps you left running in one of your spaces taking up memory, threads, and cpu for no reason. They will just get silently saved and quit, and all you will notice is that the system runs very fast despite all the background crap you have left running (or so you think). When you go back to those sleeping apps, they can spring back to life with the same windows and documents and you hopefully won't even notice what happened while you were away. Unfortunately, this only works with updated apps that are coded for Lion, but I am sure this is how future desktop OSes will all work someday.