"I thought Fallout was a rpg style affair like Diablo.."
Diablo is RPG light. Fallout is nothing like Diablo, Fallout was about having a wide open map with tons of non-linear multiple solution quests often with multiply endings. Fallout had stuff like "Childkiller - received for killing two or more children. If this occurs, a band of bounty hunters will set out to kill the player character." It was also know for a very impressive dialog system.
Fallout is very much an adult game with drugs and prostitution becoming major elements of the setting.
EDIT:
"amazing what they can do on those systems! PC version should look even better too!!!"
All indications are the PC versions are to be exactly the same as the Xbox including the lack of shadows and low textures.