Have it, and I must say it's nice. True, when walls fold there are gaps. But it's not such a big deal. You get decent number of figures, weapons etc and the walls and gates themselves look pleasant.
The catapult looks ok to me, but it reall doesn't work. I assembled it just a few days ago, just to see it again. Well I was rather surprised to see the missile just fall down instead of being launched. Back than when I first made it, I didn't even figure that it's supposed to launch using the counterweight (very probably because, as I said, it doesn't). So I made it bigger and bigger and bigger, and added the heavy bricks I got with one very old tanker set, and now it works like it should, but it's bigger than the fort.
And it even doesn't launch when that axis is removed, but it's really pulled down by a string on rotating axis, like the real thing. So it doesn't look much like it's supposed predecessor, but the concept is same, and it's certainly sane (altough badly done in the set).
Altogether, a very good set. It's nothing legendary, but still an order of magnitude in front of anything I've seen produced lately.