It's a good game that will keep you playing regardless of the gimmicks.
Let me start off with the story. The story is linear but it's solid and but can stray from the main quest at anytime to explore the wasteland. It has enough freeform and misc. quests to lengthen the gameplay by almost 12-13 hours. For those who have played oblivion you will most likely enjoy playing Fallout 3, but there are four things that you should know.
#1: If you have little patience do not play/buy this game
#2: Save ALOT (Sometimes you get unlucky and a quest-giver dies or glitches happen
#3: Rent this first because it is different than conventional rpgs in terms of gameplay
4# Do not buy this until you have xbox live or a Fallout3 GOTY edition on hand (The ending without Broken Steel download content will anger you because all your hard work will go down the drain.)
It is not the typical fps or 3rd person shooter because the creators (Bethesda) Usually work with PC/Rpgs games and some mechanics of the game are noticably recycled and some of the same flaws remain.
Examples: Character models are just as stiff as they were in Oblivion, and when your character walks it still looks as if he/she is skating on air.
Fallout 3 is unique by the fact of the VATS system that in not turn based neccessary but pauses combat (you can still take damage during the action) to allow you to target bodyparts. Nothing is more satisfying than having the bloody mess perk and dismembering your enemies with the drop of a hat. You can play however you want in fallout with your own created character.
The game is good in my opinion, but not for everyone, so don't get it unless you feel like taking a chance