Please keep in mind that these opinions are for the alpha version of the game.
End of Nations plays like a starcraft custom map. Movement and units are similar. Each unit has an ability. You have a certain ticket count of units you can have in control at once, and the number of tickets varies based on the unit. You don't build your units, you summon them to a drop point. When units die, you summon more until you run out of whatever currency allows you to buy them.
You can also add turrets to your army, which basically act as stationary units. The last part of your army is a sort of "god ability" that lets you affect an area. Mine lets me repair units over time in a green circle that I can place.
The combat is all about micro-management of your units. If you're good at micro-managing in starcraft, you should be good at this.
So basically you start the game and choose a faction. You're sent to a tutorial which teaches you how to move, capture points, and finish one gametype. There is a chat box that goes server-wide. I can see this becoming an issue when more people play. After this brief tutorial, they throw you into the actual game.
You receive two menus with several options, including Friends, mail, P2P store, Leaderboards, "Campaigns" (faction competitions), Research Tech (unlock new units) and Achievements. The two main buttons are Armory and War Room. The armory lets you customize your army, and adopt heroes. The war room lets you choose a battle to fight in. 4 maps are available in the alpha (one is the tutorial), with 3 gametypes. The largest map in the alpha is a 4v4 map, and the smallest is a 2v2.
-Capture all points before time runs out (or defend, depending on what team you're on) (points can not be recaptured after the defense loses them)
-Capture and hold points to gain score faster than the enemy (like conquest from battlefield)
-Tug of War until one of the teams bases are destroyed (like Nexus Wars in starcraft)
After playing a few matches, I've noticed battles are heavily in favor of higher level players. I'm still only level 2 after 3 hours of gameplay. I hear the game picks up at level 5. You receive exp and wealth from each battle, but winning will give you a lot more than losing. It seems the opposing faction almost always wins, and with not many players (there are about 500 people in the alpha, total), this ends up leading their faction into a very dominating role.
Credits are purchased with real money, and wealth is earned in-game. You can purchase new units/heroes/skins/mods with either of them. In the alpha, it would take about 10 20-minute games to purchase one unit. This makes purchasing via cash a much faster way to obtain the units you need. This game doesn't look pay-to-win, but cash will save you a lot of effort. You still need some skill to play the game. There is also a VIP option, but I'm not sure what this will add to the game.
Hope this was informative!