I must admit that I bought ZOE for the MGS2 demo and it is probably a game I would have rented first before buying.
I've only played it for a little while, but the graphics are awesome. So far I've not been able to beat the first boss, Tempest. The anime style cut scenes are just what you would expect from anime, the same kind of acting and expressions in the voices. Too me, the acting is very cheesy. However, I am trying to get into the story and I will play this through to the end. It is not a game I would have bought for itself, but I am enjoying it.
The MGS2 demo rocks! Even with the very little bit you can do(in comparison to a full game) I am extremely impressed and will probably play it many more times. I've already pre-ordered the game itself. There are just so many things you can do in it. I've seen people write that when you switch from the intro movie to gameplay, you can't tell any difference in the graphics. I'm not totally convinced of that, but the graphics of the intro and the game play are very close! Just sitting in the rain on the deck of the ship observing your surroundings is such an experience.
Final word: The purchase of ZOE for the MGS2 demo is worth the $50. If you are into mecha style anime stories, then so much the better. If you're like me, you may just want to expand your gaming horizons as I have been trying to do since I got a PS2. (In other words, trying some different things instead of sticking with the same genres I have always stuck with.)