Kabuto: Wow what a terrible commercial. It looked like they were promoting some kind of futuristic shooter, not a real time strategy game.
They're simply showing off the singleplayer content and the best stuff their cinematics team has made. Building probes doesn't make a good advertisement ;P.
Up until a few months ago, I treated StarCraft's gameplay as a acceptable way of passing time between the briefings and cinematics. I still am a "story guy", so the main reason for buying SC2 will be the same as it was for playing SC1 - watching the events unfold...