Comfortable, roomy, simple.
I was looking for a pack for more extensive day hikes and with the addition of the Mountainsmith strapettes, I found a pack for multi day lightweight treks. I like the simplicity of the inside and the bright yellow interior. Many companies make a big deal out of all of the cool organization pockets inside their bags but in fact I almost never make much use of them so the simple open design is more useful. The weight distributes well and in my test hikes I determined you can use this pack to carry in the low 20 pound range at least for the beginning of the hike.

Strapettes Required!
This Mountainsmith lumbar bag I received from Altrec and its great. Two comments to help you with purchase: it is with one large compartment, and only a tiny pencil-cased size interior compartment other than the large main compartment, plus one exterior pocket. I agree with another review here about benefit to a single large compartment in most lumbar packs, but with the overall size of this one, itd be improved to have several inner compartments as its hard to dig for belongings when its so deep. As an aside, the water holders can be used as compartments (e.g sunglasses) because of their nice fabric, not completely see-through. Some lumbar packs have straps only for waterbottles--this fanny pack's more utilitarian. Second, this pack requires a set of Strapettes. The shoulder strapette is mandatory because, even completely empty, the top of this pack leans away from your body. The hip belt is at the bottom of the pack, so without the straps, there is no top support. The hip belt, in my opinion, should have been placed at the middle of the pack for better weigh distribution. That said, the Strapettes work very well with this pack, they are comfortable and make this fanny pack great for day hikes. Much less sweaty on the upper back than a traditional day pack (but a traditional day pack is preferred for warmth in fall/winter climates, however). I wish the manufacturer had added tabs/velcro on the back of the Strapettes to attach walking sticks, carabiners, etc. as, unlike a full sized pack, there is no pace to carry these items. I will likely add some velcro loops on my own. This is a great lumbar pack for the purpose of carrying large items, day hiking in summer. Just be sure to buy the Strapettes, made by the same manufacturer