I received an awesome book from Sylvain, another senior designer here at Harmonix. It's
101 Things I Learned in Architecture School, and despite the title it actually has a bunch of really useful, spirit-raising and enlightening things about the creative design process in general:
I highly recommend it, even more so if you're doing any kind of level design.
In other news, GDC Speech is coming along. I'll probably post some small chunks of it over the next few weeks. Content reuse!