I broke down the other day and bought "Gold," the in-game currency of World of Tanks- exactly $6.95 worth. They recently went through a number of updates, and I'm actually finding that they fixed some of the gripes I had with the original, fresh out of Beta release. Yes, mid-tier tanks are still largely useless in a number of situations, but I get the feeling that things are at least moving in the right direction. American Tank Destroyers have been added, and while I can't comment as to how useful they are just yet, they've certainly managed to shake things up enough to make the game feel fresh again, enough for me to spend a pittance to transfer some EXP and whatnot to get myself into a T-34, up from the doldrums of frustration that is using the A-20. It still puzzles me that the "scout" tank has a view range of ~270 meters, while the "medium tank," the much slower T-34, has a range of ~400m with the upgraded turret.
I've not yet committed to getting back into the game full-time, but we'll see how things pan out. I'm also plodding down the German heavy tank line and the American TD line, but I doubt I'll get into the higher tiers any time soon.
Also, for what it is worth, they've hinted at "shared progress" through their upcoming games involving World War 2 Battleships and Planes, something that piques my interest quite well.