I was just about to ask a similar question, except I'm at home. All files are on the living room HTPC, but I do all my tagging/playlist creating etc on my laptop (as I'm sure many do). I used to have just the one library on the HTPC and I'd VNC into that machine to do all the work, but that was just too slow and awkward. So I created another library on my laptop, and now I use a syncing program to keep both libraries (including thumbnails) synced. Very tedious, time-consuming, and basically a pain, but at least it can be done.
I do all of this because as I understand it, if I were to keep one library on the HTPC and run library server (or one of the server type offerings), I could not tag with my laptop (which is what you want to do, but from work).
Am I correct? There is no way to run the server on one machine, but do all the work on another?