One Floor Up More Highly by Katharina Grosse in the museum's massive Building 5 gallery was also really sweet, (although unfortunately it came down January 1st):
Other exhibitions well worth the trip were The Workers and of course, the Sol Lewitt retrospective. If you get the chance, you should definitely check out Mass Moca, it's in a beautiful old complex of mills and they run a sweet hotel right across the street, Porches Inn, where you get breakfast delivered to your room! All in all, a great mini vacation.
