Three new trailers for each of the characters:
To coincide with the new trailers, new previews have been shown to the press, with a list of the newly-announced features here
The heist mechanic sounds amazing. I was expecting something similar to the casino heist in San Andreas, with several missions of set-up and one big mission being the actual heist. But from the previews it appears to be much more open-ended in GTA5. You actually plan the heist on a whiteboard, you're given a list of requirements (weapons, vehicles, disguises, etc) that you acquire as you see fit prior to the heist, you hire accomplices (with more skilled accomplices costing more), and each heist has a stealth option. The better your preparation, the smoother the heist will be, but if you spend too much money on preparation then you might not break even on the venture. What's more, your accomplices have skill levels that can level up if they take part in a successful heist with you, but if they die because of your poor preparation then you'll have to hire some rookie next time.
It sounds like a game made up of several Mass Effect 2 Suicide Mission-like sequences, but with the added bonus of sports cars and jet fighters. I really hope they pull it off.