Game's huge, awesome and full of WIN, ladies and gentlemen, yes, full of win.
I loved the game since it was not only a perfect rebuild of the whole SOR/BK series but also it brought tons of new refreshing stuff that could make up for a wishful SOR4. What also made the game refreshing in all sense is that it's not only a retell of each and every game but a whole new game that allows you to reminisce the classic games if you wish (but still with a little extra to give more consistency) or explore new, unexpected turns of fate by going in different directions.
It not only includes all the playable versions of all the characters and the hidden characters from previous games, but also new characters with new style and even some unexpected enemies joining forces. So game has tons of time to explore with the gameplay of each and every character (with revisions included) AND the huge map to go.
Difficulty it's high, even in Easy modes (which make the game playable for average skilled players), veterans with skill will find it quite challenging even to finish in hard, this is due of the speed of certain enemies (this can be toned down, in my opinion) and the use of all the skills properly (not a bad thing, certainly a welcome one since enemies in previous game didn't use all their moveset), not to mention their positioning in surrounding the player and find ways to hit in the right moment. AI in both enemies and CPU companion it's quite good and with more logic, though sometimes the CPU has little hiccups when it needs to go forward with you, but it's like minimal complaint.
Music is beautiful, obviously the reactions are mostly positive but since music it's always a subjective matter sometimes there's people who don't like it. In my own judgment, I think it's great and plenty of tracks keep the flavor from its original versions (Attack of the Barbarians, Expander, etc.) while others got a huge huge huge facelift (the whole Poets series, the Cycle series). I know there's a scheme of uploading an alternative soundtrack from the composers so guys stay tuned for more music in your game.
I haven't gone deep into the SOR maker or the mini-games but that proves that game still has plenty of things to do besides the normal beat'em up and i'm sure plenty of people would spend another huge amount of time on them.
All and all, minimum things to be refined, but that's certainly nitpicking. Game's out and delivered it with quality, no more no less.
Oh, and +1000 for the Double Dragon 2 NES homage out there... that was simply awesome!