Action Junkies - Defiance's best quality is its gunplay. It's fast paced, chaotic and mostly accurate. You'll spend most of your in-game time killing bad guys when you are not fetching items or unlocking terminals, so it's nice that Trion Worlds got this part right.
However the gunplay is encumbered by grossly repetitive mission structures, the same horrible enemy spawning found in games like Borderlands and Call of Duty and a burdensome interface that makes switching between more than 2 weapons mid-combat a serious pain.
On top of this, you have to keep in mind that this game is an MMO. MMOs thrive on keeping the game challenging for 100s of hours. So don't plan on finding or being rewarded with any shields, weapons or grenades the are ultimately devistating. This was my biggest point of contention with the action. The weapons I used during the final hours of the game were a rare sniper rifle I got from a friend early in the game and the Rifle that Nolan gave me in the TV Mission. You will not feel like a badass by the end of the main campaign unless you are lucky enough to win the lotto via the rare item drop boxes throughout the game or know some friends that can hook you up with some sweet gear.
Bookworms - If you are primarily a bookworm, don't bother with this game. The story, characters and dialog are supremely corny and uninteresting. To make matters worse, the clumsy narrative also hinders you from feeling any sense of purpose for your actions. This is yet another shooter you can throw on the pile that boils down to mindless killing with no real sense of weight tied to your actions
Explorers will be treated to a vast open world--one that gives you no incentives to explore it unless you're an action junkie looking for gun fights. How can you have wide-open terrain with nooks, crannies and buildings just begging to be searched and not reward the player for venturing out by allowing us to find rare loot?
Strategists may love and hate Defiance. I found so many combat situations that were just begging for me to sneak in from the high ground as a sniper and rain down destruction before eventually assaulting across the objective to clean up stragglers. But for as many of these situations as I found, I found at least two other missions that made me deactivate generators while trying to dodge enemy fire from spawning enemies. Not to mention the plethora of missions that make you defend a uplink station while 200 bad guys spawn out of nowhere and descend upon your location. Defiance is truly a mixed bag when it comes to strategy. Sometimes you'll love it, other times you'll hate it. Unfortunately for me, the love sequences were few and far between.
Builders - This was the second area where I felt like Defiance let me down. I bought Defiance hoping that it would scratch the itch I felt like Borderlands 2 couldn't. I'm specifically talking about giving me a more fleshed-out character development and customization system. Defiance did deliver this, but then squelched it with leveling that takes too long and limiting the amount of passive and active skills I could use at any given time.
But again, this is an MMO. If you enjoy MMOs, you probably won't gripe about this as much as I did because you'll be willing - and really used to - investing 100s of hours to get your character up-to-par. I'm a bit more impatient than the average MMO player, so take my criticism here with a grain of salt.
Collaborators - As an MMO, expect Defiance to be more fun with friends. But honestly, unless you have a group of friends who are planning to play this game with you, don't expect to link up with too many people while playing online. From my experience, most of the people in-game are focused on the ark fall events that get old after you've done five or so. For an MMO, it feels more like a single-player adventure.
In the game's defense, I will say that I believe many gamers are waiting to see how it develops over time before they jump in. So this will most likely get better with time.
Competitors - There is PVP. It is functional and can be fun. Just don't expect it to be mind-blowing and don't let it be the main reason you decide to play the game. Oh, and plan to use stealth and shotguns because you'll probably get lit up by all the other people who are if you don't
Audiophiles and Visualists - like the Bookworms, you audiophiles and visualists need not apply. The visuals border on whack and the soundtrack is all but non-existent. The sound-effects are passable and the voice-acting is less than memorable.
Achievers - Completionists should have a good time with Defiance. None of the achievements are frustratingly difficult from what I've seen and there are a ton of missions and side missions to occupy your time.
Overall - If you have not already decided to buy this game and are wondering if you should, my advice to you is to wait. Wait until better content comes out. Wait until they fix some of the bugs that have been lingering since launch and wait to see if they address any of the issues I've outlined in the review if they are pet peeves that you and I share.