Flawless, but let's address the naysayers.
The most common complaint I see in the reviews is that you can't keep the upgrades between levels. This idea defeats the purpose of designing the initial tanks and the enemy tanks, and would alter the game so signifcantly that it's a moot point.
The solution's pretty obvious: Survival mode, where you go into increasingly difficult levels with a stronger and stronger tank, fueled by your ability to salvage. Now every body's happy!