The main reason why a lot of people complain about the game is because it requires intelligence to master.
I've played this game for quite some time, playing tanks from every technology tree and I really don't understand the problem. Yes, it is true that Soviet tanks have sloped armor, which due to laws of physics allows them to gain a few hundred more mm of armor protection as the shell can no longer directly penetrate the hull, but hell... that's where your brains are supposed to come in.
This game is complicated for many, that's why there is a lot of negativism on the forums and in this game's review "box" - people don't understand why a shot from their Pzkpfw IV's best cannon bounces off the IS-4's front armor - well, there's several reasons - Pzkpfw IV's penetration power is lacking, IS-4 has sloped front armor, you need to aim at special spots, you need to flank heavy tanks if you're a medium tank, the IS-4 is 4 tiers higher and one of the most powerful tanks in the game alongside other tier 9 tanks!
American tanks... well, I can sort of agree that their armor is not definately up to the standarts of German and Soviet tanks in the game, but really - have you guys checked what the turret has? American tanks in this game have the most thickly armored turrets from all, some high-tier tanks have so well-armored turrets that even same tier Soviet and German tanks have difficulty penetrating it - that's why the term "hull down" is so popular amongst American tank players - you have to hide your bloody paper hull and let the enemy eat your turret.
And if you don't have anywhere to hide at - then rush at the enemy tank, force him to shoot at your turret - if his cannon is long enough, which is the case for high-tier tanks, then you'll be safe as all of his shots will be going straight at your turret, perhaps even at the gun mantlet which is even stronger for some tanks (mostly Tank Destroyers).
Right now it just seems like I'm defending the game, but I just don't have much to say, just pointing out the major "flaws" of the game as described by players who are here to throw off potentional new players.
Rating from me is only 8.5 because this game DOES have various issues, that I can undoubtfully admit, some of those issues include matchmaking, various major bugs appearing from time to time (like once heavy tanks with armor skirts were practically inpenetratable in the tracks, as far as I remember), getting stuck constantly in town maps on various debris that isn't mapped correctly etc.
And about the issue of heavy costs at high tiers - the game is free to play, it needs to earn somehow, so you have 2 choices at high-tier - either pay for the game OR keep a tier 5 tank to earn credits with, they're great moneymakers. Developers also constantly host various events and contests, which allow you to gain extra XP, buy tanks at lower price, win thousands of gold etc.
The graphics in this game are average, nothing much to comment. Various cover, houses, trees etc. are destructible, which adds quite a nice flavor to the game - if you see a tree falling down somewhere and you don't see anyone there - then you can know that it's an enemy tank approaching.
Oh, and also the camouflage system is quite f***** up - I once had a Tank Destroyer appear only when he was like 30 meters infront of me, which seems quite ridicilous, but doesn't seem bothersome as it's a rare occurence and according to developers - it's being worked on.
A summary of the game -
Gameplay - fun, addictive, can eventually get boring as without premium account you have to grind a lot in tanks you might not like, but that's the hard truth in all games with a leveling-up-like system.
Graphics - average, nothing bad, nothing too amazing, they're working on new physics, so that's gonna be some awesome eye candy, plus various cover is destructible, which adds some flavor.
And those who don't understand what's the difference between various tanks and wonder why some are weaker than others, instead of all tanks in the game having the exact same cannons, engine power, speed limit, acceleration, armor, health etc., then here's some tips (not describing SPGs as I don't play them much, lack experience with them to say anything) -
American heavy tanks - powerful turret armor, good cannons, paper armor.
American medium tanks - good all-around tanks, weak armor, but good acceleration, engine power etc. M46 Patton, in my opinion, outclasses the German E-75 and is on par with the Soviet T-54 (I still prefer Patton over it, thought).
American light tanks - awesome, simply awesome - the M24 Chaffee (top tier light tank) is the perfect scout tank.
American tank destroyers - the mid-tier tanks seem promising, they have turrets and all that, but they have paper armor and the late American TDs just get slower and slower. The T95 (highest tier American TD) has a top speed of 13kmh, the game will be over before you get to the enemy base, but it's still fun - it has the strongest frontal armor from all the tanks and it has one of the most powerful cannons.
German heavy tanks - haven't played them much, but they have high-accuracy cannons, alright armor, quite vunerable to catching on fire due to engine being counted as being in the front or something...
German medium tanks - they're alright, German mediums are some of the best at lower tiers, like the Pzkpfw IV (tier 5 tank) - perfect all-around tank, good moneymaker. The higher tier German mediums are just alright, more of the sniper type as opposed to American and Soviet mediums which are more of brawlers.
German light tanks - also very good at higher tiers, the tier 2, or was it 3, Leopard light tank is a very popular scout - haven't played it much, so I don't have much to say.
German tank destroyers - like almost all tanks in the German tech tree - accurate and powerful, altought they have no turrets and they tend to be slow, but for example the low-tier Marder II can mount a cannon from several tiers above, blowing any hostile tanks back to Moon when fired.
Soviet heavy tanks - the high-tier Soviet heavy tanks are monsters, very dangerous in the hands of good players, but nothing compared to German heavy tanks in terms of firepower (the E-100 German heavy tank has monstrous cannon and armor). Their sloped armor bounces off a lot of shots from the front.
Soviet medium tanks - some of the best in the game, including the tier 5 T-34, which is a great moneymaker alongside most tier 5 tanks in the game. T-54 was infamous in the game for very long period as it was called the most OP tank in the game, but as people learned how to combat it - it became a normal tank, even thought it hasn't even been nerfed much.
Soviet light tanks - they're just alright, T-50-2 is a very effective scout tank.
Soviet tank destroyers - monstrous cannons, altought not as accurate as Gerrman sniper cannons, but very devastating with enermous firepower. Some of the late tier TDs have excellent frontal armor, their low height also gives them various advantages (German mid-tier TDs have low height, but late-tier tanks start to get big, which is their disadvantage, while Soviet TDs in almost every tier have very low height hull).