What I like about it is that it's quick to play, but also that it's kind of addictive, as you just wanna get that next upgrade, and the next tank etc.
I have upgraded to the next level of tanks, but it's kind of slow as I wanna try out all the different ones. Right now I found the Self Propelled Guns (SPG) that some call artillery and the super fast Soviet tank - BT2, to be the most fun. At least the BT2 is a fun tank that outruns most of the other tanks.