It's funny, I didn't pre order this. I wasn't sure that I wanted it, because I had played Fallout 3 and Borderlands a ton, and this looked too similar to get me interested. I have always been a fan of iD, but they hadn't made a game in so long that I didn't know what to expect.
Well, I beat Gears3 and felt like getting a new game, so I ended up picking this up anyways. I am so glad I did. The combat is perfect, and that is the main thing this has over Fallout. It's hard to explain what I mean by that, but the weapons have "weight." They feel good when you fire them, or even reload. Things like the wingstick are a joy to use and never get old. Then there driving bits; races, vehicle combat, those aspects of the game are done well, and it's impressive the way the game can mix the two genres seamlessly.
I have spent over 10 hours on disc one alone. I keep doing things like the mutant bash tv over and over, and try to get the acheivements for the minigames.
That reminds me. The minigames are pretty fun also. I've probably spent at least a couple of hours between them and little side missions like the postal run or sniper cover.
Anyways, if you're on the fence about this game, like I was, you may end up being pleasantly surprised with all it has to offer. In the "post-apocalyptic" genre, it's a breath of fresh air.