I never knew that humble had a deal to get into the CB. I'd have jumped on that. I'm especially jealous because people who played at least X number of games in CB got a free Arizona class battleship.
Having played through to the battleship, I must say that I am very VERY impressed. The graphics are really good (though I may turn them down a bit to take the fog out of the distance), really VERY good, the physics are awesome (Firing a salvo with the battleship displaces a heck of a lot of water, just like in real life), but I'm wondering about the viewing distance. They've gone into INCREDIBLE amounts of detail in nearly every aspect but two: One is that it doesn't seem that they've taken the curvature of the earth into account. The other is that the guns on the South Carolina could shoot about 18km (and up to 25km on WWII battleships) in real life, but the game restricts me to about 10km. I'm guessing that's for fairness' sake, though.
The game isn't for everyone, though; my friend gets really frustrated with it. It's worth it to give it a try, though, I promise.
You start with both an Erie class American cruiser and a Hashidate Japanese cruiser. They play very similarly, but may fool you into thinking that the rest of the two nations ships do, as well.
Initially I chose America while my friend chose Japan. The American Tier 2 and 3, though, are quite different from the Japanese Tier 2 and 3.
The American 2/3 ships are a bit slower, but the guns load much faster. The Japanese ships are noticeably faster, but the tier 2's guns load much much more slowly. Fortunately, when you upgrade your hull, you are given a total of 4 extra guns to the 2 extra guns the American tier 2 is given. I earned the tier 2 Japanese ship because my friend was getting frustrated and I wanted to understand why, oh boy did I find out. The guns on that tier 2 Japanese ship load so slowly that it made getting hits and therefor xp very tedious. Once he got to Tier 3, though, that changed.
The Tier 3 American ship is a St. Louis class; to use a crude comparison, it is like an old wooden war ship. A bit sluggish, but she has an 8 gun broadside and the guns reload SO FAST. I love her to death.
The Japanese Tier 3 name escapes me at the moment. It may be Tenryu, but I think that's the tier 2. She gets 4 single gun turrets for half of the broadside but she has two triple torpedo launchers on pinions so they can fire to either side. The guns load much faster than the Tier 2, and my friend says that at half ahead, she goes as fast as the tier 2 at full ahead. That said, he still seems to have more problems getting XP with her. The torpedoes have long range, but they're slow, so hard to hit people far away; though he's sunk a battleship at close range with a full broadside.
Like me, he is also going the battleship route, and I'll be extremely jealous if we reach tier 10, because he'll be sailing a Yamato class while I'll be in a Montana.
I say I'm going the battleship route... Now that I've bought my first battleship, I'm not so sure. I've got an 8 gun broadside, still, but they fire in pairs and it takes a full 30 seconds to reload each turret. On top of that it moves like a pregnant cow with short legs, so the many and near constant atoll maps are ridiculous when trying to line up shots.
All ships get a repair ability to put out fires and repair damaged turrets, screws, and rudders, but the battleships get a heal ability to go with it. Both have a 2 minute cool down and the heal ability has 3 charges.
If you go the battleship route (or the Japanese tier 2 route) don't fire full salvos until you get your eye in. Test fire from a single turret to make sure that you're leading the enemy ship enough; once you get your eye in, you can let them have it.
There is also an auto pilot mode, handy for my battleship since it takes me forever to get places and I've got half a minute load time. You bring up the map, click a destination and shift-click to add waypoints. The game will take care of the rudder, you just control the speed. Putting your screws to reverse or attempting to steer will break the autopilot, though.
Lots of people drive with their binoculars on, so there are occasional collisions and groundings. Keep one eye on your minimap and one on your target.
Approaching torpedoes don't always come with a warning. If you're vigilant, you'll see the little (very little) red torpedo indicator on your hud, showing you the direction from which they are approaching. If you're not, you'll get a pinging sound to let you know that you're about to die. Generally if you hear the pinging, manoeuvring to avoid them will be quite difficult.
XP is gained by hits, sinking doesn't seem to get you a very big bonus, just a notch on your belt. The most XP I tend to receive are from citadel hits, or hits to the command superstructure or conning tower. Very rarely I'll punch through into a powder magazine and blow a ship with a single salvo, most of the time you'll be pounding on the other ship for a while before it goes down if you don't have torpedoes, even if you're in a battleship.
Leveling can be slow, but once you hit lv 4 you'll get 3k free xp to research your ship, hitting lv 5 will net you 750k money to buy your next ship.
That's all I can think of to share, right now. :p
=edit=
Ah yes. Aircraft carriers. You can work laterally along the tree to unlock them at Tier 3. From what I've read it seems that they play a bit like an RTS. You go into map mode, launch your planes and send them out via waypoints to look for targets. You've got torpedo bombers, dive bombers, and fighters. So far I'm always glad to see a fighter wing in the air above me so I won't have to worry about torpedo bombers. You'll want your torpedo bombers to approach ships perpendicular to the direction of its movement, but you want dive bombers to attack along the length of the ship.
Destroyers.
I haven't played with these yet. They are small, quite fast, very nimble, and always equipped with torpedoes. They have guns, but it doesn't seem to be their focus.