It's not something you're packing up to bring to Patagonia or Tibet. But it's great for what the name says, hauling stuff from your car to the campsite. At the SAC price, the two smaller bags are a pretty good deal, very versitle in and of themselves. But then you have the hauler as a bonus! The hauler can hold a *lot*, and the large opening makes it great for big, bulky items.
It's better than the Mountainsmith hauler because the Kelty hauler itself zippers up so it can be used as a big duffel, while the Mountainsmith is just a open-top bin. The Mountainsmith seems a lot more sturdy, but then again it's also a lot more expensive.
The Kelty material is a little thin, and the derlin frame means it can't be rolled up for storage. And because it's large and square(ish), it's not the easiest to carry around. But for the SAC price (under $20), it's an AWESOME deal!