We are primarily a Linux shop (currently Debian; probably Ubuntu in the foreseeable future) with a lot of the sort of quirks you’d expect from an MIT lab (AFS, lots of homegrown stuff, people with root on their workstations, etc.). We also have lots of Mac and Windows machines, and the person in this position will end up doing a fair amount of supporting Mac and Windows users, as well as Debian desktop support and system administration.
Our departing sysadmin (leaving for grad school) hopes to have some overlap with the new hire. He has an excellent and patient way with users, good documentation skills (internal and user-facing), a desire to do things the Right Way that will save us work down the road, and the gumption to take on substantial projects, and we'd love to have similar qualities in his successor.
(I forgot to mention in that mail that I’d love it if we found somebody with experience administering email on Linux/Unix systems, since I’m the postmaster and if we don’t I won’t really have a natural backup/collaborator for that. We use Exim, SpamAssassin, ClamAV, Mailman, and some homegrown stuff and have a slightly quirky email topology. That’s all optional, though.)
If you’re interested, you should definitely fill out the online form at that link, but you should also contact me (email if you have it; otherwise comment here or direct message here or on Twitter) so that I help make sure your résumé doesn’t get lost or delayed.