When I first removed it the plastic "skirt" at the bottom had slid out, and just looking at the metal part I thought "Hey, they put it in upside down!"
Then I tried to figure out how to put it on "upside down" while still retaining the plastic part, and realized it was in the right way. Just a bad design.
I thought about sloping it, as well. It was all caulked-up at one end (where the door opens), so that there was nowhere for the water to go; at the other end (the hinge side) it was left open-ended. Maybe it was meant to be sloped a bit, but that would collect the water in that corner. Outside the shower, near that corner, I've got some water damage on the wall, just above the trim. It's possible that they didn't properly caulk it at the bottom, on the inside of the shower, or it could be that there is a small leak above, where the enclosure connects to the wall -- and then the water runs down the inside of the wall and gathers at the bottom, causing damage.
I'm just not sure, but now that I've started on it, I'm going to caulk the hell out of it, everywhere. Just saw a razor-thin gap in the caulking in one of the shower corners -- wasn't there in the summer, but maybe with the change in weather it's opened up. We've had water damage in the kitchen ceiling below the ensuite. Builder's been in a few times to re-caulk the shower, bottom of the tub, fixed some small gaps in the grout in the tub surround, fixed the ceiling -- but I don't think they ever got all of it. And now they won't even return my calls.