Starts slow, picks up around level 5 and ends up great. Action in spades, don't let R.P.G. give you the what evs.
I was initially frustrated with the lack of ammo and constantly searching for something to load my gun with. Not a scavenger, I resorted to hitting beetles and ants over the head which was extremely against my grain of play style as I'm more of a caster than a melee guy. I was becoming frustrated enough that I thought about uninstalling and never looking again.
I pressed through my urges to remove this game from my hard disk forever and started finding ammo and getting enveloped in a very well crafted game with atmosphere and good writing. From 3 dog updating your latest exploits on the radio to killing super mutants with creative tactics I found myself really enjoying the game and wanting more.
I won't go into great depth as there are enough reviews out there to give you that but I will say this game is very well worth playing and don't let the RPG piece scare you off. You don't have to use the famous VATS system, you can just blast your way through fps style. I actually found the VATS system to be very inefficient for me, probably lack of points in the right guns, but I would miss things right in front of me with VATS and hit them head on without. VATS for me became more of a nice bullet time effect to use when I was getting bored rather than a counted upon tactic.
Fallout 3 - Highly Recommended.