The demo was the first to feature the engineer class (the one I played), in addition it was no longer as boxed in as the previous demo at comic-con. The action was solid, and I only encountered two errors;
1. Upon deploying my first turret, the game froze and they had to completely restart the system.
2. If said turret is deployed next to Mordin and "the asset" it will attempt to destroy the "asset: with it's flame thrower.
Improvements were numerous including an updated combat drone with a much more detailed model. Also, surface refletivity worked much more fluidly then in ME2/1.