I've played a few beta matches, and so here's my 2 cents worth. Only played the allies and japanese briefly, not fully in depth, so I might change my opinion. The favored side right now seems to be the Soviets *cough*Apocalypses,Kirovs and Dreadnoughts*cough* so I look forward to playing that side.
The Allies move fast, and can take the tempo of the match early by spreading out fast. The peacekeeper is a pretty tough cookie, and in a maestro's hands its a wonder to see. Their armor is severly lacking, necessitating tactics greatly. Their supposed air power is a bit over emphasized; their only combat chopper was the .... **********. Suffice to say its incapable of actual combat, but is a interesting unit to say the least. The Apollo air fighter works as well as advertised, but its quite weak, so picking your targets is important. The mirage tank, is a wonder. But it needs to learn to stay still at this point in time. Their naval power is ... awesome. Carriers, amphibious destroyers, dolphins, hydrofoils. Their hover transports are viable combat threats too, packing a heavy MG and torpedo launchers. But soviet subs can really take a bite out of your navy. Important use of abilities is paramount. Oh. They lack a dedicated AA defense, irritatingly. But IFVs make up for it in a pinch.
The Japanese are ... different. Note that building a structure produces a unit, which you then order to unpack somewhere. Their primary defense can switch from AA to AG, which is handy. Never got a chance to explore their navy fully, got FUBARd in record time. A good strategy is to rush tankbusters. They tear through armour incredibly fast. Ironically, the Japanese also posess the ultimate counter to an early infantry rush: a samurai! Their basic infantry can switch from a pulse carbine to an instant kill sword. Most of their units are inspired based on sterotypical japanese stuff, so expect to see Macross look alikes. Before you ask, I never got to use Yuriko or the King Oni.
Overall, the new naval aspect is totally game changing. I wiped out a guy's base, only to lose because he had relocated his base off on water, and he hit me with dreadnoughts from the rear. Previously naval control was not really an issue; now its very important, not the least because of the ability to build naval bases.