I own a 3L version and love it. I haven't had a leaking issue and the suction required to drink from it is very comfortable. The only thing that I gripe about is the ease of filling it up. Unless I'm missing something fundamental you have to hold it vertically, but since you're filling it from the side you end up stopping early due to it wanting to fall over. It's a minor annoyance, an I've yet to go backpacking somewhere where water is a real problem to come by so I can't say it's ever been a hindrance.
And that flat back makes it super easy to just slide into and out of your pack.