Fallout 3 walked so that this game could run.
The developers, even with insane time constraints were able to make a masterpiece of an rpg using old assets from Fallout 3. This game took what was bad about Fo3, fixed it, and made the good parts better.
However, the game has its gameplay issues and bugs, but what game made on the creation engine hasn't.
Overall, this is the best Fallout title to date, and is definitely worth a look if you are an rpg fan, or overlooked this one because it wasn't made by Bethesda.