Bit late....World of Tanks went live a few weeks back and is free to play!
Quite a fun game as well. If you like tanks and also like camping in games I highly recommend giving it a shot!
It's based on a micro transaction system so if you want to earn the higher tier tanks quickly you can buy ingame gold which gives you access to premium accounts and specialized tanks, faster crew training etc... Otherwise you can get access to almost everything without paying a cent.

One benefit of this game is you can have multiple tanks and as soon as one is destroyed you can jump straight out of the battle and into a different tank and battle without loosing any points you earnt in that 1st battle. This is a good method if you want to earn credits quickly as you can have 4 tanks(without having to pay for more garage space) that you constantly switch behind.

Tanks consist of Light, Meduim, Heavy, Tank Destroyers and Artillery(or Arty as they call'em).

If you're a light, Meduim or Heavy you can gernerally roll into the battle shooting up other tanks while also spotting enemy for the TD's and Arty to hit from afar!

I prefer Tank Destroyers myself and like finding a bush and hiding in it until enemy tanks are spotted and I then help wilt them down.

Arty is fun. You basically sit near your home base and you get an overhead view from which you can rain fire down from!

All tanks have quite a few upgrade options and you also use these upgrade paths to work your way through the tank tiers!

Last but not least....one advantage of WoT is that playing a Teir 1 tank is as much fun as playing a teir 6 tank. While there are the occasional balance fails but it's all good fun as everyones generally of similar level so you've always got someone that you can shoot in any particular game!