I've been gaming for decades now and this is no doubt in my top 100 of all time (perhaps even top 50)
No question is a di-rect decendant of Fallout 1 and 2 as so many here have stated. What more can you say to that?
It is amazing already and it's not even finished yet.
-Crafting of guns, armor, electronics, grenades, chemicals, even ammo
-Deep ability/skill customizaton options to play the game the way you want to play
-Export an existing character to be used a new game (that 'trick' can help with the harsh difficulty level)
-Heavy on exploration with a 'far from home' feel once you venture far enough out
-Wide variety of enemies and hostile situations to challenge you
-A fun and creative range of combat options (kneecap shots, crippling melee blows, setting on fire (hells yeah), knife throwing, even psychic attacks
um not much...
-steep difficulty curve, unforgiving at times (you need to learn what armors protect best in many situations)
-not a lot of personality to the dialogue at times (though it has improved a lot)
-a lesser sense of a 'real' community in the towns (not much going on in the background)
If you're a fan of old school turn based RPG's....you owe it to yourself to check this out. This is an experience you should not cheat yourself out of.