The mighty MacBook Pro was upgraded to Leopard mere hours after it was released. Always nice to live dangerously. Especially after I got bit last time by the Tiger upgrade when Apple changed the IP stack so that my Cisco VPN broke (and Ciso took their sweet time to fix it - weeks!).
My impressions so far are....
Overall a nice upgrade, the system in general feels more responsive. Spaces is a great addition for someone like me who constantly runs ~15 apps. This works brilliantly when running vmware in full screen mode in one space - I go from full screen os x to full screen windows with a quick ctrl-3 keystroke. Nice. There are some spaces wierdness though. So far I have lost Thunderbird completely (disappeared from all spaces and could not get it back) and Eclipse mysterious had its title bar moved beneath the system menu which made it incredibly difficult to move back on to my workspace.
Time machine is very clever. But the disk I/O kills my laptop if I have the external disk connected all the time, probably because during compilations etc I change a lot of files regularly. Perhaps Time Machine is not for a guy like me. Most users will love the cleverness and convenience of it though.
The dock blows. I like the 3D business and the folders that can be added and displayed as a fan or grid. I hate the reflections and shadows and transparency. There is too much going on and is more difficult to see each icon. I also hate the blue and white spot beneath the icon to denote the app is running. I want a solid dock with little or no reflection. The folders added to the dock get their image from the first application the folder contains. What GOOSE decided this? My applications folder has the Address book app as the first item, so hey presto I get the address book icon as my Applications folder icon. Uuuuugly.
The fan. Well it sure looks cool in the demo but in practice it blows goats. You get 9 items and it doesn't scroll. How many people have folders with less than 9 items? It is quite unusable. Either make it scroll so I have some way of getting to my other items or get rid of it. Displaying as a grid does work quite nicely however :-)
The system menu at the top of the screen is semi-transparent. If your background image (like the photo on mine) includes light and dark areas, the text is difficult to read. I don't want a menu bar I can see through thanks.
I get the feeling Leopard is more about paving the way for the future than a killer release in itself. I think we'll see a lot of tweaks in the next couple of months as Apple buckles to consumer pressure give the UI it's last few tweaks to make it very usable. Nothing above is a train smash, I just feel the UI guys missed the mark a little.