Quick answer - no. Long answer - search the forum.
I suppose you are boring talking multiuser support, sorry. Let me show as I see, multiuser for me its:
1) Password you supply in amulegui lets you change only your category (category will be similar to user for logging purposes) and you can't change files in anothers, but you can see them obviously (this is better for avoid several people trying same file or same file some different -other name or so-) This feature is independent of users in operating system or files permissions
2) There is a admin cat which can manage all files independent of categories and can manage preferences of amuled (globar preferences)
3) I'm interested in set maximum number (hard set) of files downloading/waiting and maximum for each user (soft set)
example: 2 users (A and B), 6 hard max queue and 3 soft max for user
user A with her queue: 2 files
user B with her queue: 5files (4 in queue and another stopped for hard limit -he try to start download by he can't

-)
---> now user A add another file to queue putting her link into square and clicking commit

(he not reach her limit) and user B got 3 files in queue (amule stop file with low downloaded percent)
funny, no?
For that or something similar it will be interesting:
startnextfilesamecat option in amule.conf working :p (not working in 20071212-cvs as I know)
You said EC protocol allow users, so don't think in ed2k network problems (which know nothing about multiuser in that scenario!)

Thanks for replies, I know we spend a lot of time thinking in that but currently only kind users can share a daemon and I don't know any

Feel free for explain me you point of view! Have Fun with amuled+amulegui!