I just bought a FastPack 250. From my initial tests, it appears it will serve my needs very well. I don't think there would be any problems fitting a Canon 40D + grip and any reasonable zoom lens. The Macbook Pro should fit into the laptop compartment (I don't own one myself to check). My kit is: 30D, 70-200 f4 IS, 17-40L, 35 f2, 60 2.8 macro, 430EX. All of these fit comfortably, and one of my important criteria, that any lens should be able to be mounted on the camera at any time is fulfilled.
One nice thing is that unlike the default configuration (which you can see in the pictures in the other thread), I was able to configure the bag so that I can access all the lenses while the bag is hanging on the left shoulder.
I will try to post a review shortly.