Of course I had to have it.
The game would be released in two editions: the 'normal' edition and the Wizard's Edition, which would have a plushie of Mr. Drippy (the High Lord High of the Fairies, one of your companions, who starts off as a doll!), two small pieces of DLC and a physical copy of the Wizard's Companion, a book that is used in the game. Of course I ordered the Wizard's Edition, and I was one of the lucky souls who actually got their order (because there were much more pre-orders for that edition than there were copies).
I have finished the game some time ago now. In short: I liked it a lot, but I don't think it qualifies as an RPG. It is scripted too tightly -- you can't choose to play as a bad guy (and face the consequences) like in Baldur's Gate or Skyrim. You can't even choose which stats to increase when you gain a level. There is a ton of sidequests, which you should do because of the perks you can gain from completing them, but they're really side-quests that do not advance the plot much.
The game is easy, if you are a bit careful as to where to go next. Monsters don't level along with you, so if you have to visit the first town again later in the game, you're ridiculously overpowered compared to the monsters. (Most will flee away from you, but there are a few die-hards in every field that will run towards you instead -- but they quickly find out that they still aren't a match for you!)
There is a large Pokémon-like aspect going on, with you gaining familiars (either by conjuring them or by winning over defeated monsters) and having to level and evolve them. The puns on the names of the monsters are pretty bad, though. (What to think of a vampire-type monster called 'Ex-Girlfiend'? Or a single super-shark called 'Lone Shark'?)
But what makes the game shine is the plot. It is indeed epic, and there is a lot of back-story going on that is only gradually revealed. Once all the pieces fall into place, you get an all-encompassing story that goes back eons.
And then, when the last battle is done, you get a lot of post-game content. I understand that's a thing these days, but I do not understand why they didn't include it in the game proper. Still fun to do (if you enjoyed the side-quests), but I did refuse to endlessly grind a particular type of monster because I need a particular type of ingredient because someone wanted me to make a particular type of weapon through alchemy.
I finished the (almost-)complete game in about 55 hours. It can be done faster, but I did take my time doing things. If you like the plots of fantasy anime movies, then you will like the story and appreciate the obvious Ghibli-ness of the designs. If you consider yourself a 'hardcore gamer' who only cares for FPS'es, then it should be obvious this isn't for you.
(During the weeks that I played Ni no Kuni, the Skyrim DLC for PS3 was released -- each with 50% off initially. So I bought all three and am now doing a new play-through. Again as a Bosmer sneak-archer, because that's just what I am. It's interesting that I'm enjoying the ride, even though I do know what's to come (except for the DLC, of course -- I'm doing the Dawnguard quests right now). I'm overwriting save-games from January 2012 -- more than a year ago, and I'm now almost as obsessed with the setting and the game as I was back then.)