Snow Leopard is installed on both my MBP and Mini.

One of the minor new features I think is cool is the ability to minimize an application to its dock icon rather than next to the trash can (System Preferences->Dock->Minimize windows into application icon).

I have never been too much of a fan of task switching via Cmd-Tab. I never really liked Alt-Tab on Windows either. Since I use Spaces pretty frequently, I have a tendency to just click on the dock application icon to switch to the space that the application is running in. With Expose being "exposed" on the Dock, it has made navigating even easier.

So far I haven't had really any major issues. It seemed like it took a lot longer to install Snow Leopard on my MBP than on the Mini. And once I had it installed Spotlight indexing churned again sending the CPU and fan activity way up. However that was only for 15 minutes or so.

Overall it has been a pretty nice upgrade so far. I love the fact that I got 15 GB in HD space back on both machines. When was the last time you have upgraded an OS and actually gained GBs of space?