Yes, simulation is actually completely core to the gameplay. It's not really an option to play the game without running simulations, as you will die constantly from unexpected sources. But because it's such an integral part of the design, it's all good (not to mention close to unique -- you almost certainly haven't played a game like this before).
I thoroughly recommend watching the first impressions video made by Total Biscuit, as he really impresses upon you just how fun and engaging this feature is.
Then try the demo when it comes out to find out for yourself. But do watch the video first -- nothing else I'd seen had actually made me understand how important the the simulation aspect was.
I've all but completed the single player campaign now, and it pretty much rocks. I haven't even had a multiplayer game yet, and it's already been well worth the money.