I am NOT missing:
1. The Finder - I love the new multi view Finder, especially Column View
2. The App switcher - Love the Dock and its customization
3. The old Apple Menu - Love the new 'System' centered Apple Menu, and Docked folders
4. Memory Management - for obvious reasons
5. The 2D UI - Love the 'depth' of Aqua and the revealing animations
6. Old graphics engine - Quartz is truly fantastic ( I have my monitor resolution pumped up as high as it can go. Text and photos look incredible. Photos, in particular, have an unbelievable sense of realism, almost 3D effect)
7. The way a single click of the mouse stopped everything
8. Launching & Quitting applications all the time - I almost never shut down, and I almost never quit my regularly used Apps
9. Application layers - love the interleaved windows with the ability to bring all windows to front with a click in the Dock
10. The speed of 9.x - 10.1 is just as fast
11. The old DVD player - X's DVD player kicks ass
12. Alert, save, and printing panels DEMANDING & REQUIRING my attention - Bouncing icons, sheets, and muti-tasking rule
13. Mouse dependency - I like being able to perform a lot more tasks from the keyboard, constantly having to move from keyboard to mouse isn't necessary, the keyboard is an input device just as much as the mouse is
14. One size fits all icons - not only can you scale your icons, they're also freakin' gorgeous (or at least, can be)
I can go on and on...
I am obviously in love with OS X and Aqua!