It has alot of driving in the game, so I can understand that. I wouldnt worry to much, the game will most def play well on PC, iD wont let us down. Remember that this is developed in house. 2 DvD's with install will give us everything we need, the game is quite large, the 360 version is the one that really suffers from just 2 DvD's, as they wanted to try and fit it on 3.
Overall I hope to see the game in action at quakecon this year, because I love iD, but am iffy on the game in general. They are branching out, which is always good to see from a company, and I am quite interested to see the first product of iD Tech 5.
Best,
3Ball