It's a FPS game with some RPG elements, like leveling up, a few skill point choices, and the questing aspect. It's a shooter before anything else though, rest assured, there is nothing but action, action, action. The only thing I can think of that you might not like is that you do level your proficiency with weapons, which increases damage and (I think? mike can confirm/deny) your accuracy with them. However, for the most part, if you have an enemy in your sights, you are going to hit them.
It's not like Fallout 3. People got that impression from the local the game is set in. This game is much closer to something like Halo or Call of Duty (albeit in a different setting) than it is Fallout or Oblivion. It's a stretch to call it an RPG, it's an action game.
For what it's worth, I haven't seen a single person say they didn't at least like it, and most people I've talked to really love it. You will like it. I said this earlier in the thread, and I'll say it again, and I really mean this, it's the most addicting/best game I've played this year.