Well I picked this up today, gave a few Campaign Missions a run through. Haven't attempted Multiplayer yet (I hate playing any game's MM Solo). Based on Campaign though, I enjoy the game.
So far visually the game is gorgeous in campaign, and there is 2 different perspectives to play through (Security Forces - Protect the Ark, and Resistance Forces - Escape the Ark) Pretty diverse weapon selection and all too. You unlock Weapon Mods via "Challenges", which have you playing through a particular scenario and you can get up to 3 Stars, with each Star unlocking one or multiple weapon accessories.
As you get kills and achieve objectives in Campaign you gain EXP which helps you level up. You unlock more weapons/character accessories/outfits based on your level. Customization is pretty in-depth for a FPS.
You have the choice of playing as 4 Players Classes; Soldier, Operative, Engineer, Medic. So far I've noticed no real differences between them other then special abilities. You seem to have the same amount of health, and you can use any weapon with any class. And like how EXP unlocks clothing and stuff, you also gain "Ability Points" which can be spent on upgrading/buying more special abilities for each class.
You can't change class on the fly but you can change at your teams "Command Post", you can also view objectives, and change weapons there.
Ummm thats all I can think of so far for the game. I'd personally give it a 8/10 without any MM at this point. But I will update this once I play some MM later tonight.