In no particular order.
1) USB Printer Sharing
2) Software Base Station
3) Finder Labels
4) Spring Loaded Folders
5) FTP capability through the "Connect To" (Apple-K) option in the Finder. Make FTP volumes appear like regular volumes on the desktop (ala Netfinder)
6) I'd like to see Apple make a general purpose Twain scanner driver, like what they did for Image Capture. This way in the future scanner manufacturers can just use Apple's solution instead of having to devote their own resources in to writing drivers.
7) Better power management features on Powerbooks
8) Return of sounds in alert boxes and dialogs. Of course, it will need to have an option to turn it off too.
9) Better dock options, for instance A) Allow us to turn off the labels when we mouse over items in the Dock, B) Make the item names that do show up on Mouseover have a background, (like those yellow MS tool tips), so the text of them is distinguishable from text on dekstop icons. and C) Give us the option to make the Dock encompass the entire side of a screen that it occupies, regardless of how many items are in it. Have the Dock items flush left, with new ones added to the right.
10) Speed increases (10.1 is good, let's shoot for even better optimization in 10.2)
11) Bug fixes - here's my list of most requested bug fixes
a) Get icons on the desktop to stay put in their assigned positions. I find that with my dock on the right, my icons keep creeping over more to the far right of the screen. I keep having to manually move them a bit left so the Dock's text doesn't confuse text from items on the desktop.
b) Fix the damn multiprocessor Quicksilver deep sleep issue. I'm wasting $$$$ keeping this thing awake when I'm not around it because deep sleep doesn't work on it.
c) Improve Mouse speed resolution. The highest setting is too slow if you have a monitor any bigger than 1024x768, which most of us do now. And while your at it, improve third party USB 2 button scrollwheel mice support. It's OK right now, but if Apple isn't going to give us the 2button scrollwheel mouse themselves, I'd like to see them at least fully support 3rd party solutions a little better. See #12...
12) Fix it so that Carbon applications Open/Save dialog boxes can take advantage of scrollwheel mice.
That's all I can think of now....