... So far I'm really pleased with Leopard.
Everything worked perfectly after installation and migration.
I like the look and feel, and things generally seem more responsive and solid than in the last incarnation.
And I haven't even started using the new features yet. Nice.
And Apple has finally fixed two issues I've had with the the Desktop Picture ("wallpaper") control panel:
1) You can now have several folders of images sitting ready for selection, instead of having to hunt around for it whenever you wanted a new folder.
2) And now it will fit an image to the screen even if it is portrait-orientation and too tall for the screen. It drove me batty for seven years that I had to go to Photoshop, edit and make a new file to make this happen before. :)
Update: I did not know why "Spaces" should interest me, since I use keyboard shortcuts (macros) for changing between apps. But it turns out Spaces works on the single-window level. So now in one browser I may have a Blogging Space and a Reading space, and a Web Admin space. Each with a couple of windows. (Sub-update: in a rapid turnaround of events, I have abandoned Spaces for now. They seem to cause a little too much confusion both for me and the OS.)
Update: Thanks to Through The Lens for pointing to this review, which supports my feeling that a lot of good work has been done in the deeper levels of Mac OS X with this release. Quote: "As I've learned more about Leopard, it's become increasingly clear where, exactly, those two-and-a-half years of development time went. Leopard is absolutely packed with improvements. It seems that not a corner of the OS has gone untouched."
I recommend this e-book bundle.
Ooh, by the way, I accidentally bought two copies of Leopard. Anybody want to buy one? Fifty pounds or a hunnert bucks.