Short answer, it's worth buying if you enjoy Fallout as is right now, but it's fairly messy. It's good. Really good. Well thought out and gracefully executed. Many of it's aspects feel natural and drive you deeper into the lore and immersion. Only caveat is that the coding needs much more time to work out the kinks. There's seemingly random crashing, quests acting up to the point where you can't progress without console commands (which tends to further break the quest), some areas (even relatively small instanced areas) tend to have a huge FPS hit.
