There are lots of things I like about school work. (And silveradept is right about the teaching license - though if you do what I did and go for independent schools, you may not need one. Some of the Catholic schools locally require one, some are happy with the MLIS, and most of the other independents want either the school library licensure *or* the MLIS.)

I'm not as sure how the market prospects are for rare books and preservation - I suspect not as horrible as the profession as a whole, but that there aren't still a lot of jobs out there.

I should probably do the ramble on the three limits of getting a library job sometime soon, too. (Location, type of library, and focus)