As I say, "Solid", but a little repetitious...
Art-Style (Graphics) - Since this is one of the first things presented to you, I figured I should cover it first. It's definitely unique and really attractive to look at. The cell-shading(esque) look and feel to it hit me right out of the box, and I really liked it. Te environment is attractive and well represented (post-apocalyptic "scorched earth" setting). NPC characters are well-represented and the monsters/enemies are cool. However, if you want 8 billion shading elements and enhanced tri-linear antistropic-whatever realism in your games, this may not be for you. Still, in my opinion, you really shouldn't pass it up just because of that.
Gameplay - It's definitely a shooter, and that is the primary focus, but it has a nice little RPG element thrown in to it with skills and abilities that you can adjust as you gain levels. As a big RPG-er, I think they could have compounded on this and fleshed it out a little more... But, I figure that might have bogged the game down and taken away some of the "slickness" this game offers -- a sort of "get in the damn car and put on your seat belt!" feel (i.e., the learning curve for this game is pretty minimal). Besides, I figure if they had focused more on the RPG element, they may have been called out for creating a Fallout clone. Also, it offers multi-player -- both co-op and competitive, I think (not much of one for multi-player, so I'm not too sure if BOTH are available, but I do know that "co-op" is). Anyway, from what I've read the co-op can be a lot of fun, if that's your bag.
GUNS! - This should be included in with "Gameplay", but it's a MONSTER element in this game, so it needs its own section. What can I say, other than "Holy Crap!"? This game is a bonanza for looters... Guns on top of guns on top of even more guns. Enemies drop a boat-load of loot in the form of various guns, shields, cash and other items (class-specific boosts). Think of it as Diablo II on Jolt! Cola (Not quite "on crack", but a slight step above). Same kind of formula as Diablo II -- lots of unique weapons dropped (and mind you, a lot are junk).
The Buggy - Cool little "mini-game" aspect in the game. Guess it's not really a mini-game, but it's a cool diversion, as well as a nice, quick form of transport in a relatively big world. Customize the color and gun type (.50 cal or rocket launcher -- I recommend the rocket launcher), jump in the driver seat (and if you're playing multi-player have a buddy jump in to the gunner's seat) and hit the gas... Mow down unsuspecting baddies with the gun or just flat-out run 'em over (the latter is A LOT quicker, by the way). Fun, but again, after a little while, it can get kind of repetitive.
Sound/Music - Cage the Elephant's "Ain't No Rest for the Wicked" hits you straight away in the intro (which I recommend that you watch in its entirety... It's actually really good). Music throughout the game is great -- a kind of "twangy", desert-style (if there is such a thing), fits the mood and environment perfectly. The voice acting is spot-on and believable.
Replayability - Definitely has it. This is a game that I could leave installed on my system and go back to again in a few months (or even a few years) and still play.
Bottom-line - Great game and a lot of fun, with good replayability. However, it can get a little repetitive.