Excellent.
I loved just about every bit of it. Great concept, great gameplay, great game. When H.G. Wells wrote "The Land Ironclads", he must have imagined something like this. I only found a few weak point in the game, bringing it just short of a 10.
First, i found it too easy to screw up the configuration if the tank in the heat of battle. Often i found myself rotating a gun into an unusable angle or tossing it off the tank altogether. Beign able to pause the game and reconfigure the tank at my leisure would have been much better.
Second, picking up spare parts as you go is a hassle too. massive, oversized tanks tend to block the pieces and make retrieval a chore. It would have been much more fun had I been able to pick up the pieces more efficiently. Being able to make tanks transparent to pick up pieces behind them could have solved the problem.
Lastly, I spent more time reconfiguring the tank than I did piloting it. Th game is 40% blowing stuff up with an awesome steam-tank and 60% putting the tank together. Perhaps being able to save configurations and load them at will would have been nicer.
Despite its flaws, the game was fun on so many levels. Nothing is more satisfying than blowing a gun off an enemy tank and then finishing them off with it.
For improvement, maybe more varied guns, the ability to zoom out the view for when tanks get too big, and more affordable upgrades are the only things I can think of. If you plan on making another, might I suggest a top-down view for added mobility, and perhaps allied tanks as well?