As for the Atmos, I loved the fit of the pack, but… (1) The curvature of the main compartment might be difficult to work with. Is this true? (2) It’s design is too complex for me to mod and personalize. (3) It’s the typical common ‘hot’ pack right now so it lacks uniqueness. (4) Some of Osprey’s design sensibilities are questionable IMHO- too many zippers and pockets and straps; too much weight. But the pack looks good overall. And it’s available at a local store with lowest-price matching. And I’ve never tried any other pack that felt like donning a pair of wings. [/quote]

Dan, you can slide a bear canister into it very easily with room on the sides to stuff clothes and such, so in my opinion, the curvature is a very negligible hindrance. If you wish to compress and narrow the pack, the straps will do that. Loosening them all the way makes quite an
opening. In fact, when the divider is taken out, you can put a large bear canister crosswise in the bottom of the
pack through the sleeping bag compartment flap.. This makes it carry well and leaves lots of room for other gear. As for the weight- it's a quart of water heavier than UL packs- in my use- basically NOTHING. I'm really not an Osprey salesman; for me and my purposes they got this one right. I looked at the Buttermilk (thanks for the link), I liked it, especially as it has the large pocket on the back. In my experience, (which started with one of the original Kelty external frames) I'd rather have extra capacity than too little. But it really comes down to how the straps and belt fit you. I hate packs that feel great with 20-23 lbs. then you add 12 lbs. of water and the shoulder straps turn into belt sanders. Make sure if you test out packs to load the thing HEAVY and leave it on for awhile. There may come a time when you need to carry more than you thought or would have liked, and your pack shouldn't be a huge pain. OM is right, Daisy has a lot of good advice, don't discount it, you usually have to buy a very good book or somehow pay for what she offers freely.