One of the strong advantages of this game is how beautiful it works -- the way the gameplay works, the beautiful graphics, the simple but challenging way of playing different tanks, the ease of play (no cockpits or headgear required!). A lot of complaints are about match-making and tanks being "nerfed" but these are easily remedied by a subsequent patch if the devs feel it is worth fixing. Most match-making complaints hold no water anyway -- as it is a MMO, the match-making program has to work with what it has at the moment... unless players are happy to wait for half an hour for a "perfectly balanced" match.
MadDog, German TD-wise, the Marder II kicks ass, then goes downhill from there. The Jagdpanzer IV suffers the same as the Stug III in terms of matchmaking --- you'll be surprised if you dent your opponent. I think I ricochet 80% of the time, so switched to HE rounds. Better a little damage than none at all. Having said that, once you finish the JgPz IV, the JagdPanther simply rocks and you'll be able to whack 20-30% off from most tanks you come across.
I've learned that the fastest way to get the next tank is to NOT sell your elite tanks. When you do your daily double XPs, each elite tank can get 900-1200XP (on a non-Premium account). Whatever tank you're grinding only gets that double XP once, then each subsequent battle gives you less XP. Even if you grind your highest tiered tank at the moment, all that 900-1200XP from elite tanks do help a lot. Imagine one elite tank, played just enough to get one win each day (thus get the double XP), will have at least 6,000XP by the end of the week. 5 elites and you have somewhere around 30,000XP!