Are you looking for a bag that can hold two cameras (even with a 70-200 2.8) and allow you to access either of them readily? If so, check out the LowePro Slingshot 302 AW.
I have two cameras so that I can quickly use different focal lengths, without having to resort to using a superzoom lens (all the compromises that entails). Usually, my Nikon D300 is equipped with a standard zoom (Tamron 17-50 2.8 VC) while my Nikon D70 has my tele zoom lens (Sigma 50-150 2.8). I also like to carry two (or more) speedlights with me.
I was quite pleased with my previous camera bag, the Targus SBM200 backpack (reviewed here). Besides being almost half the cost of the similar LowePro Slingshot 202AW, I found that the SBM200 (and presumably the 202AW) could be configured to carry both my cameras while still allowing me to access either camera readily. Unfortunately, the Targus was not very sturdy. It suffered a couple of ripped seams within just 3 months of using it. It was still serviceable but it looked worn and beat up, and my wife was asking me to replace it.
|One of the ripped seams on my Targus SBM200|
The 302AW looks well constructed although I would not describe it as premium quality. I will update this review after a few months of use to see how well it holds up.
The 302AW has a capacious interior. In the default configuration, the main compartment can fit a camera with a lens plus 7 more lenses or speedlights. If you're willing to go with 6 lenses or speedlights, then the camera can even be equipped with a 70-200 2.8.
My preferred configuration is to fit it for two cameras. As you can see it has no problems whatsoever and could fit even two cameras with 70-200 2.8 lenses.
The top compartment is also very roomy. Whereas I struggled to fit two speedlights in my old Targus, this one easily accommodates 3 speedlights, with ample additional room for other accessories (perhaps a TTL cord).
My favorite feature is the tripod holder (pictured above with a Targus TG-P60T tripod). The tripod holder was added to the slingshots with the -2 model name (so the 100, 200, 300 and 350 won't have a tripod holder). Unlike the Targus, the tripod holder is located in a way that doesn't prevent the main compartment from being opened even when a tripod is attached. Unfortunately, I don't think it will be possible to use the holder for anything larger than a medium-sized tripod.
The 302AW has other nifty features, such as this built-in all-weather cover that slips out from under the bag (hence the "AW" designation in the model name). That could come in handy not just for rain but also sand in the beach and other harsh environments.
Another feature that I like is the dedicated memory card holders in the flap of the main compartment. The holders are large enough to fit Compact Flash memory cards. The flaps make it very easy and convenient to switch memory cards, which can sometimes be hard to fish out of a larger pocket when you're in a hurry.
The 302AW does not have a laptop compartment. For that you'll need the Slingshot 350, but the 350 doesn't have a tripod holder. At the time of this writing, there is no Slingshot 352.
The slingshot was designed to be able to swing quickly in front of you for quick access to the camera. Unfortunately, that requires a compromise in the ergonomic design of the backpack -- it only has one strap. That means the load will be borne primarily by one shoulder, and it can get tiring (based on my experience with the Targus). I have to admit I'll be tempted to bring a few more accessories with this larger bag so I'm guessing it will be even more tiring to carry this. However, the bag does come with a waist strap that distributes some of the weight to the hips when you're trekking and don't need to quick access to your camera.
One of the comments I've read about this bag is that because it's so big, it's hard to swing it forward for camera access, unlike its smaller siblings, the 202AW and 102AW. Although it's definitely bulkier to swing forward compared to my old Targus, I personally don't find it bothersome:
Brazilian jiu-jitsu! :-) ]
So far I'm pleased with this purchase. I'll update this as I continue to use it.