Knock wood, mine work fine so far. I have a 3-gal. one in the coop and a 5-gal. one in the yard. The 3 gal. one is hanging (oops!) and the 5 gal one is on bricks. Sometimes water dribbles over the edge for a few minutes, sometimes the water level is only about halfway. I figured it was barometric pressure or something. A little while longer, it always is fine.
Taking off the outer sleeve: I carry it over to the hose, turn the outer sleeve so it is lined up to pull straight off. Tilt the can and let the water in the lip run out. (This breaks the vacuum, I think.) Then lift off the outer sleeve.
I only fill ours about halfway. I figure after a day or a day and a half, my chickens want cool, fresh water. Any longer than that and the under water surfaces start to feel a little slippery, and I figure it might not be the most hygienic. (Of course these are animals that peck at everything, even pooh, so...)