I've been playing the game for a couple weeks and really like it but there are some flaws in a variety of areas. I'll list some pros/cons
Pros
Graphics: For a free to play game the graphics are surprisingly good. Being Unreal Engine 3 this is somewhat to be expected. The game is very presentable with the maps and models looking good and having a degree of variety.
Item system: This is where the game excels. You get to customize your character with helmet, torso, and leg armor which changes up your speed, HP, stamina, HRV recharge speed, headshot damage reduction, and equipment slots. You then get to select up to five pieces of equipment with one being a tactical item (heal injector, revive shot, cloak, etc etc) and the other four being melee weapons, grenades (frag, HE, EMP, shock, digi, and toxic), and mines. Finally you get a primary and secondary weapon and get to customize barrel, muzzle, stock, magazine, and scope plus color and tags. This leads to a great deal of available weapon tweaks with every piece usually having pros and cons. Do you want a assault rifle with high damage and range with incendiary ammo at the expense of high spread or do you go for a much more stable platform with lower damage and perhaps EMP ammo for slowing hardsuits?
HRV vision: The importance of this tool cannot be underestimated. It is the single biggest addition this game contributes to the genre and allows for a much greater awareness of the battlefield. If properly used it allows you to better plan an assault or counter one, recognize a flanking opportunity or again counter it, and identify dangers. Failure to use it will get you killed by someone who does take advantage.
Mixed
Map design: The game has a good variety of maps but there are a few that have areas that need to be tweaked and have more routes through. Some of them have areas that are a bit too advantageous in certain game modes like domination or king of the hill. There is a map in a sort of china town where the first king of the hill spawn is put on the roof of a tent market. A team can make capture progress while hiding in a a second level stall that cannot be shot through from the three sniper perches in sight of the rest of the area or even by someone standing on the point. You have to go up and around or lob a grenade in from a corner on the bottom level.
Weapon types: Like in other shooters there are some weapon types that are superior to others either because their own stats are too powerful or the stats on the other type are underpowered. Assault rifles and SMGs are an example of the latter. Assault rifles can easily be built to have absurdly low spread and very manageable recoil. SMGs on the other hand have absurd spread values with both hipfire and aiming and the recoil statistic, despite being lower than assault rifles, results in less manageable shots because you have to deal with more horizontal recoil than AR's have. The times I've seen ARs outshoot SMGs at close range is rather silly. But for the most part the balance is good for other weapon types.
Cons
Underused ammo types: A recent patch did a small amount of tweaking to address this but it still has a ways to go. As it stands the elemental ammo types aside from incendiary are underused because of how they're designed. Normal ammo does the full damage listed in the weapon statistics, incendiary deals 70% of listed up front then 40% over time, with weapons that do low damage dealing the DoT faster and high damage weapons (like sniper rifles) having a slower DoT. Toxic ammo is like 60/50% over 10 seconds and partially clouds enemy vision as well as dealing even more damage to people infected previously. EMP ammo is 90%+20% against hardsuits, turrets, etc etc. Unfortunately hardsuits have 15,000 HP so unless you're hitting their weakpoints, and even then that 10% extra damage isn't going to add up to something meaningful, and while EMP ammo does slow the turn speed of a hardsuit it is rare that you'll be in an area open enough to take advantage or be able to corner a suit without his team killing you. And this doesn't even take into account depot items like armor stingers, flamethrowers, and man-portable railguns which are many times better at taking on hardsuits. Most ammo types, aside from incendiary, are barely used because of these facts. Statistically it is far more advantageous to bring normal ammo for most weapons since usually it will allow you to finish a fight still alive as long as you have good aim where elemental ammo will usually kill a target -after- he kills you, resulting in a simple kill trade.
Armor and equipment separate from weapon loudout: By level 5 you get two loadout slots, with the option of getting up to three more (with a cash shop purchase). These loadout slots, however, are just for primary and secondary weapons, not for armor and equipment, so you can't have one loadout slot be an ultra-speedy armor set with a fast SMG and a second loadout slot be a suit of tank armor with a mid range assault rifle.