I was there for the Bauhaus exhibition which is amazingly comprehensive and housed in a suitably plain, angular, boxy gallery. It tells you everything, although you do get the impression that it was all a bit humourless (despite the creatively themed parties and beautifully designed invitations). But it's a wonderful exhibition if you are at all interested in C20 design, and the highlight was the discovery of Gunta Stölzl who created the most beautiful tapestries and wall hangings. And there's the very good Foodhall for a very un-Bauhaus cake afterwards.
[5 Choirs Gunta Stölzl (1928) which is on display at the Barbican, but hanging the other way up]
(I'd like to go back and do one of the tours. The 'skywalks' are like something out of an HG Wells novel.)