Works well, but a bit of a pain to clean, and durability can be an issue
These do their job well, but cleaning them after you get home isn't the easiest. I prefer to rinse out or scrub a wide mouthed Nalgene. Having to take the time to scrub it with a long, awkward brush, and/or use a few drops of bleach... its not worth it to me. But that's personal preference. If you like sipping on the go then the bit of maintenance might be worth it for you.
I've never personally had one of these leak or burst, since I only owned one for a few days, but I have seen them critically fail at bad times for other folks. It was personally enough for me to not ever be interested in taking a chance with them.
Also, if you like a nice hot water bottle in your bag on a cold night... forget it with these. They won't handle the heat, and I wouldn't trust one of these in my down bag any more than a mountain lion.
PS. Disclaimer - I left this same review for the Hoser, and it is essentially the same thing, just with the attached sipping tube.