I know I might be a little late, but now that most of the content has been released, I figured it was fitting to write this review which I've kinda wanted to do for a while. I'll get right to it.
I'll start off with the campaign. The campaign varies from the multiplayer aspect of the game in that it focuses much more on platforming than the multiplayer does. Everything works, with a variety of different mechanics being introduced throughout the campaign, which make up the puzzles that become increasingly complex throughout the course of the game. Now, increasingly complex could also be switched out with decreasingly simple, as Splatoon's campaign is by no means challenging, which I personally think is a shame, because the mechanics introduced in the campaign have potential for more difficult puzzles. Maybe they could've added a super challenging bonus area ala Super Mario 3D World? Regardless of the wasted potential for more challenge, the levels are generally clever, but after the campaign you are left with a feeling of "is that it?". It is deffinitely the weakest part of the game, it doesn't really shine, but it is by no means bad either.
As for the multiplayer, it is an entirely different experience. If I had to describe it all in one word, that word would be "fun!" (With the exclamation mark!), because that's what it is. It might seem complicated with all the different mechanics, from swimming in ink to refuel your ink tank, to making sure you have a safe path to swim away on, or hiding in your ink only to pop up after an enemy has ran past you then splatting him with your Splattershot, but it all is very intuitive. After the first hour of online play, you'll find yourself making all these decisions of what to do without even thinking about it. You are the squid. Okay, sorry, I just had to make a horrible "Squid" joke.
Where Nintendo fails a bit on the multiplayer front of Splatoon is with the features. You lack the ability to change your loadout inbetween matches without having to actually leave your lobby first, and then having to search for a new one. It's not exactly a major flaw, but it's such a silly thing to not include. Then there is the fact that you can't stop searching for a lobby after you have started to search for one, which, granted I haven't wanted to many times, but there have been a few times where I wish I could've done that. That was just the nitpicks though, now I'll tackle my by far biggest gripe with Splatoon:
Content
And no, my gripe is not with the lack of content, because there is enough content to enjoy, with a dozen (literally a dozen; 12) maps, tons of weapons and four (so far) game modes. I wouldn't go as far as to say there's an abundance of content, I would at least like a few more maps. Anyway, as I said, the issue isn't lack of content, it is the availability of it (or something like that, I'll explain what I mean). There is a so called map rotation, with two maps in the rotation for four hours. And if you wanna play a couple of hours, playing the same two maps over and over again can get a bit boring. Even if Nintendo doesn't get rid of the map rotation entirely (which I would prefer), they should at least expand it to four maps to get a bit of variation. Then there is how modes work. First of all, the only mode available in non-ranked play is Turf Wars which is incredibly weird. Second of all, the modes for ranked rotate in the same fashoin as the maps do, except there is only one mode in each 4 hour period. So at any one given time you only have two modes available, Turf War, and whichever mode is in the ranked rotation. In addition, you also only have in total 4 maps available (two from the regular map rotation, two from the ranked rotation). If you can only play at a specific time, but when you fire up Splatoon you notice that you either hate the maps in the rotation or you hate the mode for Ranked, then tough luck.
It's like Nintendo has made a system that makes it feel like there is less content than there is.
Final verdict
Ok singleplayer, marvellous multiplayer, stupid design choices that can annoy you at times.
Arbitrary score that doesn't mean anything: 8.6 "Too much ink"
PS: Please tell me what you think about the actual review. I may or may not do some more of these, so I'd love to know what I do right (if anything) and what I do wrong.