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Firefall is going to be love or hate for a lot of people. What you're about to read is fairly sloppy list of the notable points of this game, both good and bad. I will include my opinions, but I will not judge the game as a whole. Lets get the most glaring issue out of the way, to begin with.
Yes, the game is having technical difficulties at present. These may range from nonexistent (to those who play at low player load times) to extreme or even crippling (those trying to craft at peak times). Most of the issues in the game now are load-based, as I experienced few bugs in closed beta. However, I feel these issues will likely be resolved very quickly, if for no other reason than they will drive away sufficient players to bring server load down to a manageable level. It's better to look at the actual structure of gameplay, when you're making your decision.
Firefox is not a quest hub MMO. Its content structure is probably the first major love-hate element. Yes, there is a small tutorial to get you started. After that, you're unceremoniously dropped into the world, and from there, you're going to be doing either dynamic or player-generated events. These _mostly_ boil down to thumping (essentially a timed point defense mission which gives you resources) or ARES missions (dynamically-generated missions with kill/retrieve type objectives in open world areas). ARES missions are varied enough to be interesting for at least a while. There are other types of content, though. The primary enemy in this game actually can take territory, even large cities. If they're unopposed, they will gradually take over the entire game map. Retaking territory or defending it from attacks is something you can do. There are also high-end instances, which you can create a onetime key for using high-end crafting materials, which is one of the few things in the game which isn't open world. And there's a "boss" type monster you can go after, though I feel this isn't particularly fun or useful.
There's also PvP. It's interesting but not great, which I actually feel is major problem. If I want shooter PvP, I have a few shooters on my desktop which do a far better job of it. Some people definitely like it, yes. In my opinion, though, the mechanics are just a hair shy of being sharp enough to feel like a competition-quality FPS, and the balance is not really all there. So if you really just want class-based FPS PvP with jetpacks, either Global Agenda or Tribes: Ascend do a better job of it. But if you genuinely enjoy the core game of Firefall and want PvP as a secondary content type, it's pretty solid.
But yeah, despite everything I just listed, if you're a "hardcore" MMO player looking to "do everything," you may find the game repetitive after a while. This is partly just the nature of the game. It's a sandbox. That's how they are. The game doesn't try to generate artificial variety to keep you playing. You either enjoy the real gameplay, or you don't.
And the gameplay is really the high point here. Firefall's run and gun mechanics, as well as use of verticality and jetpacks, make it quite fun. I never got bored of the actual shooter part of the game. The difficulty is about what you'd expect. Pure MMO players with no shooter experience might find it too difficult. As a person who primarily plays shooters, though, I actually found it on the easy side.
You will probably need some shooter skill. Your class will not carry you. This game _looks_ like it has tank and healer classes, but it's absolutely not a holy trinity MMO. These frames are not nearly as specialized into these roles as you might think. Yes, the tank is durable, and the healer can heal, but they won't do either of these things with the kind of effectiveness you're used to from traditional MMO's. In fact, in open world content, while biotechs can do quite well (I like their weapons more than anything), their actual healing isn't that useful. You can heal some, but the game is designed such that players can and should take care of themselves. Healing only really shines in PvP.
The crafting system will also be love-hate. It's click and wait with only 2 slots in your queue. If you want to build more than basic items, you have to research them. Basic research or crafting will be really quick. More complicated stuff, or refining a lot of resources at once, can take a fairly long time. I've hit queues of a few hours when I've been refining a ton of midrange mats. These progress even when you're offline, though, and you can refine a ton of mats at once if you're smart enough to research advanced refining first, so you can pretty much fire and forget a ton of stuff at once while you sleep. So it's not a huge timesink. It just takes patience.
I do feel it's overly complex, in certain ways. There are tons of resource types, and each type has multiple quality levels. However, in _most_ cases, the game functionally treats all of them as only one of three types, so the quality and type becomes more important than the specific resource name. Whether you consider this convoluted or a nice fluff element is up to you.
Item durability has been brought up before. This is not really that big of an issue. It's only really a pain when you get random "purple" gear from drops. This is not endgame loot, though. Please don't get confused. Most of these weapons actually come with both advantages and disadvantages compared to stock gear, and they're designed for relatively short use. Purples are not, "Here's your Magic Sword +5 after putting in a ton of effort." It's more, "Here's some weird weapon we randomly generated which we're giving you for the Hell of it. Enjoy." The actual straight upgrades are mostly earned through crafting, and these are typically both fairly easy to sustain and are minor enhancements to stock gear.
I guess that brings me to the world. Firefall has one of the best designed open worlds I've ever seen. It's interesting, and it's beautiful. And even if you ignore the fast transport, which I did for a long time because it didn't exist in early testing, you will see every square inch of it much quicker than you think. It's a big world, but it's not as big as it seems. I think the game will eventually start to feel somewhat claustrophobic to some players. Not all, but there will definitely be some. So if you enjoy it now, you may not after a few weeks.
I guess I should mention the cash shop/pricing too. Their prices are a little too aggressive, imo, and I typically dump several hundred into F2P cash shops every year. This is at least the case if you unlock frames by buying the raw currency, which are over $10 apiece. You could just spend $100 to buy the current starter pack which unlocks all of them, and you'll get a bunch of currency for cosmetic items on top of that. You may or may not consider that a good deal. The only thing about the cash shop which I really dislike is how you can spend currency to instantly finish crafting queues. It's a very small amount, but that almost makes it seem worse, as if they want you to regularly do it. That choice seems kinda like a cheap shot from the devs, especially considering the really high-end craft/refine/research queues take a long time.
If you're not a super hardcore player, you will probably have to go to the cash shop if you want to play all of the frames on one character. Unlocking frames by using pilot tokens (the in-game currency for doing so) is much more grindy than it seems. Pilot tokens rely on frame advancement. You can get a bunch early on by simply unlocking all of the low tech tiers on all of the starter frames, but doing this will only get you access to 2 advanced frames. Then you need to unlock the advanced tech on frames, and this takes a _lot_ of XP.
That actually gets into one of the core issues of the game. It's a sandbox. Progression starts quick, but it then gets fairly slow. And after that, it gets _really_ slow. So if you're playing purely for the progression, it will wear on you. This is about what you'd expect from a game of this type, but some people might find it off-putting.
I'm going to spare you any kind of final judgment. This is more of a "what to expect" list than condemnation or praise.