Well.... I ordered a Fastback 200 and it looks like I'll be sending it back.
It's a really nice bag. It's made well. Has some nice interior pockets. Seems comfortable. But it's just not going to work for me size wise.
All I was trying to pack in the main compartment was my d200, 70-200vr, 17-55, 35 prime, and my 10-20. Everything was just a tad too tight. I took the battery grip off my d200 and it still was tight fitting in the bag with the 17-55 attached. The 70-200 was on the very bottom and didn't really fit but I shoved it in. Forget about lens hoods all together. My Sb800 flash would have to flop around in the unpadded top compartment along with my epson p-5000, because if I put it in the main compartment I would not be able to fit all the lenses. If i had my 70-200 attached to the camera I wouldn't be able to put it in the bag without swapping to another lens on the camera first. Not cool.
In use, you take your right arm out and swing the bag around to your left side. This is good for accessing the camera but not much else... safely. So I don't really see much of a point to it.
In reality, my Kata R-103 fits everything I want to take more comfortably. It does have to be completely removed to access my gear but it does have a quick access door that lets you quickly grab just the camera so your additional lenses and other gear don't fall out. The Kata is also built a lot better, better materials, has way more protective padding, better shoulder straps, is more configurable, has loops on the outside for attaching stuff, has a chest stabilizer strap... in a nutshell it fits my stuff and is pretty much bombproof.
The 300 may have worked better but I'm not sold on the way you access it as being all that helpful... not enough to justify the cost of another bag anyway.