So many sleepless nights...
After about a week of barely sleeping at night, I've only completed a handful of quests, despite the fact that I have easily put about 25 hours into the game so far. The exploration alone is so addictive that I keep telling myself that I'll go to bed "just after I find out what's over the next hill." I love it. The crazy amount of customization that's available is great, the visuals and sound are among the best found in modern entertainment of any form and the over the top violence is too much fun (make sure you get that perk that has enemies exploding into gobs of bloody goo!) At points, this game reminds a little of Bioshock (another of my favorites)- it has the same great atmosphere and feel to it, just with oodles more depth and detail.
The bottom line, this is a top-notch game and if you avoid it because some Fallout fan says that it isn't true to the originals - well, that's your loss.