I can dual and triple log on XP just fine and I have a P.O.S. old computer. I did install 2 Gigs of RAM on it, though, so that's probably why it works with a minimum of lag.
I found no issues with switching user too fast or anything.
The only issue I have is, if I quit out of the client on one of my two secondary user accounts while Maple is running on any other account, I get a BSOD from EagleNT.sys failing and a memory dump, "system has recovered from a serious error" when I restart, and I can't shut it off from the BSOD except by a hard, pressing-the-button turn-off.
I've read up on it and it's one of the Hackshield drivers. Apparently, quitting the client closes it and then the other client freaks out and crashes my comp.
It doesn't do this when I quit the client from the account that I installed Maple on.
Any fix suggestions? I've thought of reinstalling Maple, because my last clean reinstall was when the other two accounts didn't exist. But I always have to reinstall Maple like 2-3 times to make it work, and I don't have the hard drive space to keep an installer around, so I have to redownload it.

So, um... any easier fix suggestions?
I don't get the error if I just shut down the computer when I want to quit, so all 2-3 Maples get closed at once. But that's rather inconvenient for EXP pendant bonuses and whatnot. I would just leave them all running, but I can't Zakum while multi-logged without bad lag.
So... to answer the core issue, yes, it works... mostly.
EDIT: It's easier to use 2 computers because, say, if you're using it to have an HB mule, you can just go to the other computer and press the HB key. If you switch users, you have to wait for the computer to load each user account and it takes considerably more time, plus you can't see the screen for your main, so you can't pot or see urgent chats.