Black Diamond Octane

I've had this pack for almost a year and I love it. The pack is not perfect but the good well outweigh the bad. Let me start by saying the suspension is genius, my favorite so far, which is why I just bought an Infinity 60.
I am very slim, 5'9" 130 lbs and I find that some hip belts (more bulky/excessively padded) do not stay put on my skinny hips. Excessively padded shoulder straps are also a bother to me as I feel that they dig in to my bony spots more. The straps on this pack have very thin padding, and I find that this is the PERFECT blend of stability and comfort. The thin foam padding tends to mold to you as opposed to forcing itself upon you. I have never had comfort issues with this pack anywhere, and I use it all of the time.
The suspension is awesome, best I've ever worn, hands down, it will be hard for anyone else to get me to buy their packs while Black Diamond continues to make ErgoACTIV packs. This is the reason I am buying the Infinity 60, and also why I don't care about certain things on the Infinity either (such as top loading ONLY). I really cannot stress enough how comfortable this suspension is, if you are in the market for a pack, find a local retailer that sells it, try it on with some weight, you'll see what I mean... Then come back and order it from Backcountry!
Downsides:
The suspension is the best, IF KEPT WITHIN THE WEIGHT LIMITS, can't stress that enough either, this pack can comfortably take up to about 15 lbs, then the weight will start to be felt and the suspension will no longer work... at all. This is true for all packs but I feel the difference becomes extreme very quickly with this pack. Black diamond has the weight limit specs on their website, on any pack go to tech specs to view the weight limits.
The pack setup is very simple, not too many frills and thrills, top notch quality through and through, just simple. Packing for overnights would be so much easier with an extra accessory strap or two, may be even some more outside pockets.

I highly recommend you consider the Octane if you're looking for a pack in this size and price range.
My first significant hike with the Octane was a 40.2 miler in 24 hours over highly variable terrain. I have a slight angle scoliosis and my left leg is slightly shorter than my right which has always caused upper back fatigue with any repetitive movements or limitations to range of motion. Weight on my shoulders from "ultralight" packs contribute a lot of discomfort for me... even when loaded with 7-12lbs.
I am exceptionally pleased to now own a pack that is of medium volume and can handle a 20-30lb load straight to the hips (especially when your hips are not "straight") while allowing me to side-bend while walking (gecko on a window). This pack has a thoughtful and clean design without silly extras or annoying top panel lid. Weight weenies may overlook the pack due to specs but in real life I've found that sometimes this should be measured qualitatively. The fit of this pack paid for it's own weight. The stretchy side and outer pouches also increase the volume capacity quite a bit.
I did begin to feel some pressure at L3 from the belt adjusting mechanism but only when I bent down to tie my shoes. This pack can serve my needs from 1-4+ days depending on the season. Shoulder pain? It felt so good I had to find something else to grumble about.
I'm 6'2" 170lbs. The Large pack fits well.

I didn't even know that BD was coming out with backpacking packs. When I found out about the new line, I was interested to see how they were going to be. I previous experience with BD items told me that I could expect only the best. They didn't disappoint! This pack is ridiculously comfortable. The reActive straps allow your shoulders to move freely, while leaving the pack glued to your back. The Ergoactive belt pivots in a ball-socket joint which allows the pack to stay in place on your back, while your hips are moving. All the packs come in one size and the torso length can easily be adjusted to fit your body perfectly.
And at this price, it's a great deal as well. There are many similar sized packs with inferior suspension systems in the market that are going for alot more $$$.
This also comes in similar women's version BLD1164

I got this pack to use just as a large day pack; something that can handle a few layers and basic gear...as well as a summer load of 3 persons gear. It has reall performed. I can fit all the late winter early spring gear that I need in it. That includes a primaloft jacket, a fleece and an extra top layer, socks, two liters of water and food...I still had room. the outer pocket is great to just slide things into...gloves or a hat. The pack holds an ice axe well and trekking poles store easily. This will be a great summer pack hiking with the kids...load it up.The stand out feature was the suspension of this pack. The waist belt and the shoulder straps are amazing, the pack moves with you unlike any I have ever owned. Overall this pack is awsome.

i love this pack. the swivel hip belt is the best in design. very comfortable and durable. the OpenAir backpanel is great from keeping you sweating like a pig in houston. very functional belt pockets for storing cameras, cliffbars, compasses, whatevs. the construction and frame of the pack is great and not floppy. you throw it down empty and it still stands up and doesn't flop over. i'm a big fan of the compression pouch on the front of the pack. the shoulderstraps are much more comfortable then other packs i've owned and it functions almost as a front and top loader pack. this is an excellent excellent pack that is versatile and light and will keep your shoulders happy.

This pack is excellent. The suspension makes it hands down the most comfortable pack I've ever used. I was kind of skeptical of it at first and thought it might be a gimmick, but it really delivers. The difference is astounding. I bought it as a daypack, but I've actually used it more as an overnight and multi-day pack. It can fit a ton of stuff for a "daypack". The two side pockets can hold 1L nalgenes with no problem. The stretchy material on the sides so far appears to be far more durable than the more traditional mesh other pack makers use. The backpocket can hold a ton of stuff, too.