Most cinematic game I've ever played. First good Atari game IMO since Driver 2.
First off, you don't really do any direct fighting in the game. This is part of what makes this game very tiring to play. There are battle sequences, and even Shenmue style mini games, which require you to perform fast paced Simon type sequences, and others which require you to mash the keys till you just can't mash anymore. When you're walking around (not in one of these sequences), the movement is pretty basic, but what's cool is all the interaction. Like at one point you have to hide evidence before a cop walks in and catches it. Also, when talking to people, you have to choose your responses within a limited amount of time, otherwise you just say the stupidest thing on the list.
There's no physical health in IP, just mental health. Also, if you do badly enough in a battle, you just die. Your mental health can be affected by a huge variety of things, everything from drinking too much of the Cognac under the counter (across from the fridge!), to playing songs on the guitar, getting laid, anything that puts your character's mind at ease (like hiding evidence!). If your mental health drops to 0, you either turn yourself in to the police and give up on the fight, or you commit suicide (all depending on which character it is and how far into the game you are).
Classically, Atari hasn't been much of a graphics-whore, and they're not starting here, although IP does look better than some of their games lately. The graphics are just good enough to have a nice cinematic gameplay experience, but not nice enough to really wow you. The cinematic experience is enhanced, though, by a professional film director, who really does a great job of setting all the right moods with great music (even some very nice licensed tracks), and very good (not outstanding) voice acting. Overall, if you've got a nice tv with good sound, and are playing alone in the dark, you can get an experience that you'll wish you had a bedpan, so that you wouldn't even have to get up to use the bathroom!
My biggest complaint about Indigo Prophecy would definitely be the length. It's basically just an interactive movie, so the fact that it's over 3 hours is a lot, but being a game, I wish it was longer. I finished the game the first time through in about 8 hours, being pretty thorough. They could've definitely spent some more time on certain aspects of the story. There were many things the either never got explained or detailed enough, or just never were finished. It would be nice to see a sequel to the game, but the ending didn't look too promising to me.
In summation (haha, high school paper ending), I'd recommend to anyone who likes new and innovative gameplay, as well as cinematic storytelling to buy this game, it's only $39.99 new. You'll probably get a lot of enjoyable play out of it, plus all your friend will want to play (although it's not a good party game). Renting's always an option, as well, especially if you're not big into replay (LINKloco).