Fate is fantastic. I would play fate, fate, and nothing but fate except for it’s primary flaw: It’s not for everyone. To understand my rationale for that statement, I have to explain a little bit about how the mechanics work.
First off, it uses special Fate dice, the sides of which are either blank, have a plus sign or have a minus sign. There’s also a Fate card deck you can use if you prefer that and in a pinch you can use just a bunch of regular six-siders (and mentally convert 1-2 to minus; 3-4 to blank; and 5-6 to plus). You roll four dice and add to your skill to determine how you do on every skill challenge, so a character with an average skill will, on average, do average. A character with a Good (+3) skill will, on average, do a Good (+3) job with that skill (sometimes Fair (+2), sometimes Great (+4), occasionally better or worse). This makes it super easy to plan encounters appropriate for players since an enemy with Great (+4) Fighting is a match for a single player with Great (+4) fighting and a pretty tough challenge for two players with Fair (+2) fighting each.
Everything is covered by broad, broad skills (although you’re encouraged to customize the skill list if you want a more granular approach or absolutely insist on Punching being a separate skill from Stabbing) so every roll is covered by a unified mechanic that takes only 30 seconds to learn. Simple and elegant.
Where it starts to get hairy is with the concept of Aspects: a word or short phrase that describes your character, like “Surly Mercenary”, “Untrained Wizard”, or “IT Geek” (these are really simplistic examples). Each player character gets 5. At any point in the game you can spend a Fate point (equivalent to a Savage World “Bennie” or Pathfinder “Hero Point”) to gain a +2 bonus to a skill roll IF you have an aspect appropriate to the skill and/or current circumstances. So, “Surly Mercenary” might be invoked for +2 Fighting, but not “Untrained Wizard”. “IT Geek” could be used to help disarm a bomb (since the aspect and the task are tangentially involved with electronics).
On the other hand, aspects can be used against you (usually by the Game Master) for -2 to a roll. (You earn a Fate point if this happens, so failure now can lead to future success.) For example the surliness of the mercenary or geekiness of the IT guy could both be invoked against them in roll involving social interaction. “Untrained Wizard” might be invoked against the player during a magical duel t0 reflect the disadvantage created by their lack of formal education. An “I Hate Orcs” aspect could be invoked for a bonus to Fighting against orcs or a penalty to Rapport or Empathy. The best aspects can be applied positively or negatively depending on circumstance.
On top of that, you can take an action to create a temporary or situational aspect through use of a skill roll. If you succeed, you don’t have to spent any points to later call on the bonus (at least the first time). The great thing about this, is that it lets you use non-combat skills to great effect in combat and vice versa. For instance, you might use Athletics to create a temporary “I’m Flexing” aspect to gain +2 Rapport to your next roll against the beach bimbos you’re trying to interrogate. Alternately, you could use Athletics to create a “Temporarily Blinded” aspect on someone by throwing dirt in their eyes. A player of a female character once used Rapport to create an “Slowly Unzipping My Top” aspect to distract a combatant, giving her ally +2 Fighting for the round. Fate rewards teamwork and creativity. You might even go so far as to say Fate requires teamwork and creativity — and that’s the problem. Not everyone is capable (or capable of creativity in real-time; Fate is pretty fast-paced). It can be extra challenging for some folks because there isn’t a comprehensive list of situational aspects (nor could there be a list. Almost anything is possible).
In my regular gaming group, exactly half of them looooovvee Fate like nobody’s business. The others… have issues. One guy just can’t do anything quickly and prefers choosing from a menu of options over free-form decision making. He eventually got the hang of using the limited number of character Aspects but was overwhelmed by the possibilities afforded by creating situational aspects on the fly. Consequently, he was at a serious disadvantage compared to the other players and kept attempting the same skill roll over and over again — just because he couldn’t think of anything else to do (or to create a situational aspect to give him a bonus). The other players could have helped him out with some suggestions — but they didn’t because they have poor teamwork. Another player was just plain crippled by a combination of analysis paralysis and anxiety. Other game systems had conditioned him to associate failed rolls with “losing the game” so he wouldn’t attempt anything without first trying to rack up a bunch of situational bonuses. Then, he couldn’t make up his mind which situational aspect to try to create (even though they all give the same +2).
And then… you throw in Fate stunts, which are kind-of like Pathfinder Feats or Savage Worlds Edges, which allow you to bend the rules (or give a bonus) in specific circumstances. For instance: Backstab allows you to roll Stealth to attack (instead of Fight or Shoot) but only when you make a sneak attack. Hard-Boiled lets you temporarily ignore wounds. Hardcore Parkour gives +2 Athletics to move through a dangerous environment. Stunts let you make your character even more awesome… in a very narrowly defined way. There’s a short list of suggested stunts related to each skill but you’re encouraged to make up your own, which again, half the group loved and half struggled with.
I don’t actually play Fate on a regular basis (although I could because as the GM and tie-breaker, I can always vote for it) because it’s only fun if it’s fun for everyone and half my group doesn’t have fun with it.
I do sincerely adore the system and recommend that everyone at least give it a try, which is why I develop for it.