I'm playing it for quite a while. In general it is shooter, but with lots of simulation aspects. Armor thickness and round penetration is quite nicely calculated (ricochettes including). With AP ammo you have to penetrate armour first to take down hitpoints. Still there is possibility to cause some critics without penetration - damaged gun, turret not rotating etc. If you are lucky enough you can fireup oppo's tank and wait till he burns, or even blow his ammo rack - instant kill, very rare. Another thing is HE ammo causing critics more often, doing some damage without penetration. Every tank has it's runnig charcteristics like speed, turning rate, turret turning rate, reload speed, aiming speed and others. This can be upgraded and here comes RPG part. You start with smallest tank and through battling you gather cash and experience. Experience you spen to "invent" better equipment for your tank (turrets, engines, guns, radios), which you buy later for cash. When your tank is fully upgraded you can "invent" better tanks, spg's, spa's and history starts again but in better machine. You have also crew which is gaining it's own experience and lately can learn usefull skills.
To finish - i am VERY addicted to tanks and for me best game would be pure-very-hardcore simulator, but this game is so addictive that all my complains about it are long gone. I think it's worth trying for everyone.