As you are well-versed in first person shooters, I think there is a decent chance you will enjoy Bioshock. The RPG elements are dumbed-down from what some may be used to. I didn't mind because I detest fiddling with a characters stats and abilities. In fact, I found Bioshock to be too fiddly for my tastes, but since I want none, any is too fiddly.
Many have touted the story but I thought it was predictable as all hell. I've played through the "bad" ending and found the ending to be a huge letdown. I am currently trying for the "good" ending which I suspect will be a similar disappointment.
Incidentally, when going for the good ending, you receive additional bonuses that balance out the drawback of not making the "bad" choices. So, it really doesn't matter which way you choose. Just stick with your choice.
So it is a good buy. I'm not a huge fps fan and I find the full 3D to be a hindrance more than a help and I shall never get used to the controls. But for those who are, I suspect it works. The RPG elements are probably much simpler than what you may be used to. I didn't mind and actually wanted them to be even simpler, but it may bother you a little, but not enough to break the game. The story is adequate, although not as good as most say. I found it predictable and simplistic and the moral choice system is probably one of the worst implementations of such a thing. But story is really a side-issue in games. What does work is the environment. And underwater city with art deco trappings is sufficiently different that you may not notice it's the same dark corridors with lots of brown. In summary, if this is the sort of game you like, then get it as you'll probably like it. It has it's shortcomings and it is not as good as the hype even two years later would have you believe. But if you haven't learned to be skeptical of hype yet, welcome to the twenty-first century.