Obsession holds a special place in my heart because it is one of two medium-weight games (the other being Viticulture) that my wife and college-age daughter love to play. Prior to those games, we played only simpler and (to me) excruciating games like Ticket to Ride. My wife, in fact is pretty, uh, obsessed with Obsession and wants to play it constantly.
I enjoy it alot, though the point salad ending leaves me a bit flat. But the play itself, and as others have mentioned its awesome merging of gameplay and theme, far outweighs the less-than-satisfying ending. I have yet to try it solo.