TL/DR below: Getting-stuck-in-the-mud simulator. 8.5/10
In some ways this game may not be considered "complete" - but the important question for me is this: is it fun? (Is it worth my $30?) My experience thus far has yielded a definite "yes." The only "objective" is to pick up logs on one side of the map, and deliver them to another. Sounds simple, doesn't it? Even on "casual" mode - this is far more challenging than I thought, and in the best possible way. If you enjoy carefully navigating heavy vehicles through terrain they have little to no business being on, this game is for you.
Vehicles: There are a decent variety, and each has a different feel and driving style. By default, each has different equipment that serves a different function, though many are customizable and each to a different degree. Mainly, there is the cargo function, and support functions. Get your favorite truck stuck in the mud or flip it over making a bad turn? Whip out the heavy slow one and wench it out! Smash it into a boulder? Bring in the repair vehicle. Run out of fuel? There's a tanker for that. Just feel like exploring in something faster? Go find the little jeep thing stuck in the woods.
Driving Mechanic: Weight plays a huge role in the feel of driving, and once your vehicle is loaded-up, every few yards of movement become a strategic series of decisions. Should I brave that pile of large rocks or try wading through that pool of uncertain depth? Is your vehicle sure-footed on 8 wheels but slow as father time - or is it fast as a rabbit but top-heavy like a bobbing-bird? Seriously - getting stuck in the mud has never been this fun. The driving feels mostly realistic - certainly enough to suspend my disbelief, and make me feel like I'm really piloting many tons of metal, rubber, and wood through a slimy river-bed.
Graphics / Physics: This is a beautiful game. Muddy, swampy, sloshy, beautiful. Not only is the level of graphical detail very impressive, but the physics and voxel deformation match it in kind. Tires smoosh under the weight of cargo and deform over rocks. Mud squishes out of the way of your tires and splatters all over your cabin in higly convincing fashion - and it even slowly dries over time. Water reacts absurdly well to disturbance and current - this might be the most convincing 3d water I've ever seen in a game. It isn't perfect - but it's still the best I've ever seen. As mentioned above, the driving and physics thereof are not perfect, but they are better than most when it comes to off-road - and I've never played a game before this one that accurately portrays the feeling of getting bogged-down in wet river-mud. Seriously. This is very convincing gloopyness, and the splatter of mud and splash of water are of higher quality than you're likely to see anywhere else.
Gameplay: This is really all about the experience of driving these machines in this environment - that is: big heavy trucks over packed-dirt, wet grass, rivers and puddles, and of course - mud. Lots of mud. There is an objective in each map, and near as I can tell it's always the same - but as I said, that doesn't make it a simple task. There are also "cloaking points" - which are basically an alternative to "fog of war" that obscure the map, as well as garages and vehicles to discover - and in hardcore mode - to repair, refuel, and reclaim. Each map is hours of fun.
That said - my one gripe on the current version of this game is that starting a different map will overwrite the save from another - so until you finish a map, it's best to stick with the one, as you can continue after quitting the game. However, the developers have explicitly stated this will change in the next update - so hey! If this sounds like a dealbreaker to an otherwise awesome experience, put this on your wishlist and check back later. You might want to check the free tech-demo on their website to get an idea what this is like - that's what I did. I bought the game at full price, and I am not at all disappointed - $30 very well spent, in my opinon. The technology in the full game has been pushed a lot farther: every aspect feels better, more polished, and more realistic - but the demo will at least give you a feel for whether you will enjoy this style of driving or not.