@TDL: Yes, even with threading maplist takes noticeable amount of time to load and that is irritating. I've added that to our todo list along with remembering last selected item and fast key input.
Since I improved the threading the map list now loads almost instantly for me (ignoring the first time of course). I mean when I change from SP to MP in the map editor main menu, the list is populated before I can even move my mouse over to the scrollbar (before it took ~4 seconds). Maybe that's just because I have an i7 and 7200 RPM disks?
Please keep in mind, this is since I improved the threading, which should have been in the more recent demos we sent TDL for testing Tower Defence (but not in the public/balance test releases).
If we wanted to improve it further we could use more than one thread for scanning, that would not be hard and will greatly speed it up for people who have more than 2 threads on their CPU (maybe other people too due to waiting for disk reads?).
Pressing a key to select the item with that letter definitely needs to be implemented.
I agree with Krom that drag and drop is not used anywhere else in the KaM UI, so maybe it would be better to do it another way. It would indeed be a useful feature though because I often find myself clearing the queue of recruits in the barracks to add a farmer then adding the recruits back.