I have the same problem (3 desktop machines, 2 laptops). But I use way more than just Maple, so the Maple Cloud is a partial solution.
My preferred solution: a 6th machine! Seriously, I use a centralized machine which runs a subversion server, and I use this revision system for 100% of my work. Everything gets checked-in. I just need to sync up when I switch computers, and off I go. The nice thing is that this central server is backed up regularly too, and I know where the sysadmin lives :-).
As for groups, every time I start a new project (with a new student, new co-authors, etc), I create a new repository that we all share. Works like a charm. In fact, I can set up a new machine, even a temporary one, in about 3 hours so that it becomes an exact mirror of any of my other working environments [modulo non-free software].
One could of course use git, bzr, or darcs to do the same thing. I (briefly) tried 'dropbox.com' for this purpose, but really disliked it. Revision control systems do a much better job than something which just reflects your data 'onto the cloud'.
But hey, that's just me - and my 24 repositories. For Maple-centric work, it's nice to see that this new feature has convinced at least one old-timer!