Got it used, finished, loved.
The actual combat and stealth mechanics absolutely murder everything that came before it in the series, and never (or super rarely anyway) are you ever forced to stealth -- but you can, and it's advantageous to do so since knocking out targets and extracting them helps with base building.
The massive amount of customization between buidling up Mother Base and developing weapons and equipment, along with the open world-ish nature of the game does create pacing problems however, in a game whose story is kind of shitty to begin with. There are two major villains in the game, one being prominent but whose motivation and methods are baffling, and the other whose story isn't even completed (it is however, wrapped up in a deleted chapter that was available in an unfinished cutscene in the collector's edition). Also worth mentioning that there aren't any
I never formed a connection with any of the secondary characters in the game either, with the exception of Quiet (the sniper you can take on missions with you) and that was really only because of the bond formed through the actual gameplay, since she never actually speaks to you. I think had I played Peace Walker and Ground Zeros, I would have had more of an attachment to characters like Ocelot, Miller, and Paz... but I didn't. Ocelot is also just a flat-ass character who comes across throughout like a kindly grandpa, which doesn't match up with either his MGS3 persona or afterwards.
Anyway, it seems like a lot of huge MGS fans felt betrayed with the story, and specifically the unsatisfying ending, whether because of the cut content or the end twist, or both. There are already fan theories revolving around whether or not the game's lack of resolution was intentional by Kojima to simulate the feeling of a phantom pain within the player, much like characters throughout the game lament. It's possible that analysis of the game's plot and themes could yield an appreciation of them ala MGS2, but I doubt it; a lot of what's been proposed by fans in that sense is admittedly retreading ground that Kojima allegedly has done in past games already (specifically MGS2).
So having said all that, I'm not a lore whore so I don't feel betrayed, and even though the story was on the unsatisfying side and I never fell in love with any of the characters in the game, it was FUN. And as usual, the presentation is without parallel as the MGS series is typically known for. After coming off Witcher 3 (still my GOTY), everything seems so streamlined and fast and responsive, most notably how quick and easy it is to bring up the iDroid and navigate through its numerous menus in seconds with minimal delay.
That's probably enough. I thoroughly enjoyed it, but this game is not "The Missing Link in the MGS Saga" or "The Ultimate Story" as advertised in trailers. It is however, an excellent stealth-or-not-stealth-if-you-don't-wanna sandbox action game that I'd recommend to anyone.