Things I want:
1. Less bloat, no explanation needed
2. Fullscreen mode to work properly, if I do fullscreen Safari in desktop 1 with Mission Control, it should be assigned to Desktop 1. This could make it so I can have multiple full screen applications open and I can switch between them easier. Also two fullscreen applications on two monitors.
3. Notifications to do more than what it does. I think it has a lot of potential, just kind of half-assed right now.
4. Improved Safari. Although Safari is my browser of choice, I think it can still be improved. The browser market is always being improved.
5. Less convoluted UI. I feel this will be probably be done in Mac OS 11.
6. iCloud to take up less battery life. Before I turned iCloud off in Mountain Lion, I was consistently getting 3-4 hours of battery life. After I turned it off, I get more in the Snow Leopard range, about 5-6, sometimes 7 hours.
7. Finder needs restructuring. It doesn't serve it's purpose, making finding files, applications, and system workings easier. Hopefully they don't go the iOS route and completely make the under-the-hood stuff invisible, but unfortunately I feel they might.