You may not be interested, but this is far from being a "modest" upgrade of Tiger.
A brand new Finder is alone worth the upgrade. The use of Cover Flow in Finder is brilliant. I'm going to be using that a lot.
Spaces is another huge addition to productivity and organization as is stacks in the Dock.
Time Machine finally makes backups brain dead simple with little to no intervention from the user.
Under the hood you'll find some extraordinary advances. Leopard is the first Apple OS to take full advantage of multiple core processors and 64bit.
Core animation is going to revolutionize the way developers make Mac applications. With the set of tools available with Core Animation, any developer can make beautiful apps that are consistent with what Apple designs themselves.
Then of course, there is Boot Camp, a Leopard feature (even though you've been able to use the Beta on Tiger) which allows a Mac to run Windows, definitively erasing the last remaining hurdle as to why people couldn't buy a Mac (i.e. their work required that they use Windows for corporate software).
Finally, i know I'm looking forward to new Mail features like data detector which recognizes data in emails such as addresses and appointments and allows you to easily add that data to your address book and your iCal.
I also can't wait for the Notes feature in Mail. How many times did I e-mail myself something so I wouldn't forget or simply to take down a note?
Leopard is a bigger leap over Tiger than Tiger was to Panther.
The downside is that I simply cannot see anything else that can improved with this OS. It's near Gawd Damn perfect.
