glad you are excited again.
The 360 version has better looking smoke than the pc version, this has been said by the devs in vid interviews. I was amazed at how good it looked, and you're right, there is absolutely not hint of slowdown, no matter how much is on the screen. Totally fluid at all times, gotta love it.
It might seem odd that people are mentioning something as simple as smoke, but its just so cool looking in person.