As one of the authors of Legends of Anglerre, I can perhaps answer some questions about it. If you haven't already, I recommend downloading the free preview of it, and looking at the FATE3 SRD.
Legends of Anglerre - FREE PREVIEW #1 - Cubicle 7 Entertainment Ltd. | DriveThruRPG.com
SotC SRD
What the others have said is true, the game can vary significantly between groups, and requires active and interested players and GM because much of the action involves either tagging or compelling Aspects in various people, places, and things. Aspects are the most unique thing about FATE, and while they sit on a standard RPG system with skills, stunts, etc, Aspects are what set the game apart. You create your character's Aspects, and they can be anything you can imagine. They should define your character, be dramatic, and ideally be both able to be tagged (have a benefit) and compelled (have a down side). This is because you use FATE points to tag Aspects for their benefit, but you get FATE points by having your Aspect used against you. If you choose all positive Aspects, you'll quickly burn through your starting FATE points and have no way to replenish them. So something like "
Strong as an ox and half as smart" is a more useful Aspect than just "
Strong as an ox".
The environment, NPCs, enemies, magic items, etc all have Aspects as well, though some might be very obvious and some might be secret and need to be discovered. You can even create new temporary Aspects through maneuvers, or declare Aspects as a result of a skill check. Again, since Aspects can literally be anything, it requires an active group of players to think about a scene and the characters in it, what Aspects there are or could potentially be created there, and when and how to use them for best effect. There are tactics involved, and creativity, but not much moving around on a map for precise positioning. Instead, a roguish character might perform a Stealth maneuver in order to give an opponent the "Flanked by enemies" Aspect.
As for your other questions, I'd say it's about rules light-medium, 5 people is fine for a combat, and they don't tend to take all that long in most versions of the game. The "feel" is a lot more old school making stuff up with at most a hastily sketched map on scratch paper rather than detailed positioning. As for which version to get, there are several different ones, from Dresden Files to Spirit of the Century to Strands of FATE to Legends of Anglerre, and more. (The system is OGL, so anyone can use it and tweak it). Each one is different and has strengths and weaknesses, and it depends upon what you want to do with it. Do you want fantasy, sci-fi, modern day? Do you want a detailed magic system, or would you prefer rules for starship battles and random planet creation? There are sites that detail the system differences between the various iterations, and some are closer than others in terms of compatibility.