I've got one, love it. I got it for around $30 at blueskycycling.com and I wasn't really expeciting much, but it works as its designed. Let me say first, this is not up to the same quality as Camelback or North Face or the like, but for the price, its worth every penny.
First, what I like about it:
2-provides tons of storage pockets which I use on every ride
3-very adjustable and fairly comfortable
4-3 litres of water is enough to get you through any 3-4hr ride, and I ride in 90-100 degree temperatures normally without exhausting my water supply.
1-the hydration pack is made of crappy, nasty tasting plastic which hasn't gone away after over 30 uses.
2- the valve is a push pull style that pops out easily and will leak all over you if you pull too hard
3-straps don't stay secure, at least the waistband, I have to tighten it periodically during the ride or it works itself completely loose.
4-it's hot! I don't sweat much, but after the ride I've got a big sweaty oval on my back. I don't really notice it too much while riding, but after I take it off I can tell that I wasn't getting much ventilation.
I haven't owned another hydration pack, but my riding buddy has a Camelback which seems to have some better features. The water doesn't taste nearly as plasticky as mine, and the valve is a lever that can't pop off. She also doesn't have the same ventilation issues. She got hers on sale for about $40 but at the normal price of $60-$80 I'd have a hard time dropping that much over the value of the Sette pack. Overall I'm very happy, as I don't really care how my water tastes, as long as its wet, and I don't really mind sweating when I'm exercising. I'd recommend it as a first time pack, but if you are looking for a top of the line product, you might want to pass it up. I plan to replace the bladder eventually with a Camelback bag and hose because of the functionality, but I'll probably wait until mine breaks or just gets too nasty to wash. Even with replacing the bladder, it still won't cost as much as a brand new Camelback, so I say cool!