Pros: Perfect size for day trips; access contents while wearing the bag; well-organized, attractive, comfortable.
[NOTE: This review is for the "QUARTER MOON" sling, not the "half moon" sling pictured. I don't think the half moon is made anymore, and there is no listing on Epinions for the quarter moon. The QM is a more streamlined, teardrop-shaped sling bag that is smaller and much more hip-looking than the black & brown bag pictured here. It comes in several colors (avocado green, sky blue, black & tan, all black, etc.), and a smaller version (called the "crescent") is also available. You can look it up online (zappos.com has a detailed multi-view, and overlandequipment.com has a zoom view and a photo of the bag being worn by a couple of large people, for scale).]
The best thing about this bag is that you can easily access the contents while you are wearing it. You just slide it around to your left side and unzip it.
The next best thing about this bag is the unusual, in-between size: it is smaller than a backpack but larger than a purse (17" x 10" x 6"). I would not recommend it for carrying large textbooks/binders, or for really light travel (i.e., just your wallet and a paperback). It's just the right size for a walk, shopping trip, airplane carry-on, or half-day at school. You can fit your wallet and cell, a novel, lunch, and a light sweater in this thing. It hangs diagonally across your back so that you hardly notice the weight.
This bag is the perfect diaper bag when your baby is older and you no longer want to haul around a huge duffel of equipment. Here's why:
--You can put it on or take it off WHILE holding a baby in your right arm.
--You can access contents while holding a baby.
--It does not slide off your shoulder when you set the baby down.
--It actually fits in the small basket compartment of lightweight umbrella strollers like the Maclaren Volo.
--It feels light on your back.
--It is presumably easy to clean (I haven't tried yet), waterproof and durable.
The bag has two main compartments, accessed by parallel vertical zippers along the left side of the bag. The larger one (against your back) has no pockets inside, and is approximately the size of two boxes of cereal (??) The second compartment (on top of the larger one) is smaller and flatter, about the size of a hardcover book. At the back of this compartment are two zippered compartments (maybe the size of paperback books) and some pen-holders. On the strap, which goes across your chest from right shoulder to left hip, there is a small zippered pocket for cell phone or keys. This pocket is not flat; the fabric pooches out into the third dimension. On the back of the pack, there is an elastic "laced shock cord" that can be used to lash extra items (like a newspaper or sweater) to it.
--Grab-handle on the top of the bag (for hanging it on hooks, etc.).
--Padded back, covered in ventilated "dri-lex" fabric
--Adjustable waist belt (removable) to secure the pack
The pack is very well made of matte cordura nylon, not too rough and not too slick. I think it comes with a lifetime guarantee. It is a bit overpriced (about $65), but worth it because it is hard to find a bag with these proportions and with the side-access. The only other negative: a somewhat ugly logo, not a dealbreaker. If the design were SLIGHTLY more refined (i.e., the shape a bit more rectangular and the fabrics a bit hipper), this would be a really fashionable item. As it is, it is still a nice-looking bag, and above all, very functional. A serious boon for moms who need a hand free.