Some of the people I train with at the gym have bought these, and the only person who uses them regularly has really bad arthritis, so she doesn't hit hard on purpose, just enjoys the workout. She likes the way the padding feels: just enough to cushion her hand as she taps the mitt. Everyone else who has tried it (all beginners) never used it more than one workout before consigning it to the closet to gather dust. They hated the way it felt when they hit hard, and stepped up to MMA gloves within a week.

I bought this bag from KD three years ago, and it is still in great shape. It hangs in my garage (I live in Washington state), so my bag has experienced many of the things it warns you against: humidity, below freezing temps, etc. Still works great--so I'd say this is one durable bag on that alone.
The gym I train at has gone through 2 regular Century canvas heavy bags in one year, and is now on a vinyl bag. Obviously, those aren't nearly as durable (in my experience, at least). Also, all of those bags we've gone through at the gym (as well as any traditional heavy bag) have that annoying feature of being too soft on top and too hard on the bottom. This bag is the same density all the way up and down, and it gives the same smooth resistance wherever you hit it, whether it's a jab or a jumping knee. (Small caveat: I weigh 170 lbs, so I have no idea how it would stand up to a flying knee from a 250+ lbs-er!) Bottom line: great bag to hit, very durable, great price. If you only buy one bag, I'd recommend this one.