The amazing 4K screen in the foyer showing sintel.
David Revoy's mypaint demo had some excellent tricks. Including the brush context picker (Shortcut key w), which actually picks out the brush, layer, and colour used to make the stroke under the cursor. Very usefull looking and not a feature I was aware of.
Andy Goralczyk's live demo, featuring him speed modelling set to music. Really great to watch, I believe Andrew price recorded it so it should appear online at some point.
A demo of openCL accelerated compositing for computation heavy nodes such as colour grading and defocus nodes.