Sorry for the delay in response.
Yes, it does leak a tad, however with that said, I believe it would be a fairly simple fix if you really wanted it to be weather tight. It doesn't seem to let water in from the sides at all as well as at the tailgate end. The main leak sources seem to be (as far as I can tell) from the corners at the end that butts against the cab. Each corner has a very small pocket that water can penetrate the flap seal that goes from the cover to the part of the bed that runs perpendicular to the cab window. Like I mentioned, if you really wanted to, I'm sure you could get creative (and I may at some point) and fully seal it by fixing those corner gaps.
Other than that, I'm sure if you take a pressure washer to it, it'll leak more. But my observation of leaks has just been from a decent amount of rain that we've gotten over the last couple of weeks (sounds weird to even type that living in SoCal... But I swear it's true, we got quite a bit!).
Also, by "a little" leaking, I'm talking MAYBE enough to get a standard water bottle HALF full and it's really just at those far corners. I don't have the spray in liner so it's been easy for me to track the leaking.