I've been playing the PC version. I'm about 80% through it.
Bioshock rocks. Period. But it's one of those games that has such a great deal of depth, that isn't always noticed the first time through. A lot of people are saying there is so much you can do in this game, the first time through is almost a learning experience, and the second time through is when you really get it all.
From some conversation somewhere...
IMO, the demo definately isn't enough to give you a real sense of the gameplay later on ingame.
I was 4 levels in before I really started to 'get it'. There's an amazing depth and variability to the available strategies, that you don't fully realize or have access too until you've gone through a bunch of the game.
I'm probably 3/4 of the way done, and just now realised the full potential of playing the game stealthily.
Learning to use the Big Daddies as your allies, learning to hack all the security devices in the area to work for you before you engage the splicers, learning to set up traps and ambushes, learning to fully utilize all the tonics and plasmids to your greatest advantage... The depth of what you can do is not readily apparant at first, but amazingly deep once you discover it all.
The demo doesn't come close to showing any of this; it seems to merely give you a taste of the environment.
I definately recommend really getting to know this game at least once. If you decide you don't want to play it again (although this will have amazing replayability), the price you paid will be well worth the ride you got.
I would say this is far superior to Half Life 2, in terms of 'what you can do' with it. I compare it to HL2 because it has that same "stick you in a completely different and massive world" feel to it; but the linear gameplay of HL2 becomes glaringly apparent after playing through a few levels of this. This has an RPG element to it that will keep you coming back to try things in different ways, over and over.
This is definately a great gaming experience. Not very many shooters have this level of depth, variety of gameplay options, and replayability. Not to mention an awesomely bizarre atmosphere that makes you want to explore more of it.
If you ever played Dead Rising on the 360 (a great game) this has many similar aspects of that gameplay in it. Lots of weapon variety, lots of gameplay choices, lots of cool atmosphere.
Go get it. It will take you 3 or 4 levels to figure everything out, and you'll suddenly go "Holy Crap, I get it!", and you'll want to restart the game with your new understanding.