Game is surprisingly good If your a fan of tf2 or just action games in general i would recommend it.
When you first start the game you go through a short intro level that has you escaping from a prison and sets the base for the storyline and acts as a tutorial teaching you the basics of the game. After you beat it you go into the dome which is the central hub where all the various shops are to purchases items and upgrades. You can leave into the desert which is where you will go around doing the majority of your quest which will help you level up and don't really feel like too much of a grind and there are the pve and pvp missions to mix things up and help you level up as well.
The game has some fun pvp modes that are fun to play but eventually get receive. The pvp mode is called mercenary and consist of 10vs10 mp matches it has a few different modes one plays like tf2 control point battles where one team is defending while the other attacks as well as a payload style game mode where you move a cart around and a ctf type one but in reverse that involves a large mech that you have to escort to the other side of the map at the enemy spawn while at the same time preventing the enemy team from doing the same. Last but not least there's a king of the hill type of game mode but with 3 points and you try to hold as many as you can to build up points till one team reaches the limit. The PVE missions are dungeons where a group of 4 fights against AI controlled enemies making their way through it using team work and helping each other out and at the end you fight a boss and any minions that spawn to help him its fun and on the higher difficulties is very challenging.
As you gain experience by completing the sp quests or doing pvp or pve missions you level up and are able to allocate them into new abilities which you can reset for free as many times as you want so you can try different types of builds for your character to see which one works best. You can use better armor and weapons as you level up and there's a crafting system in place to add some minor enhancements to weapons and armor. And the big focus of the game once you get high level is AvA where you join a faction (the name for guilds in this game) and compete on a persistent map for ownage of sectors on the map these play like the pvp matches but your competeting for more territory for you faction or defending it a sector that's under attack.
The graphics are nice nothing really spectacular and some of the levels can be bland in their design but the particle effects look nice and the lava map looks really nice. The game seems a bit unoptimised as big battles will bog the fps down to the 30's and I'm running at 5770 1G with a i7 920 2.66ghz and 3g of ram in dx9 highest settings minus ambient occlusion at 1920x1080 no AA. Given the level of visuals I don't think it justifies it. But if you turn the setting it should run well as a wide range of pc as it is UE3 which scales well.
All in All it's worth giving a try, the game is fun to play and its only real flaw is lack of content on the amount of quest which just abruptly stop and the leveling starts to become a grind later on.