Totally worth the wait.
This is my second review of the game but thats because I have played it for 3 hours already and I am impressed with the quality of this game.
Love the secret medals, the songs are all awesome (they are all so good I don't have a favorite, unlike the other SCGMD.) the boss fights are epic, so are the guitars, the menu is very original and the animations are great.
So, since I played all the other SCGMD games I have a lot of practice in this game and while it is still hard, its certainly not impossible. I even played few songs after many tries just looking at the stcikman and not the notes (because I remembered them already) and got a perfect.
I give this game a 5 and I think it should be more. Even if it can be frustrating for some people, if they practice enough this is going to be one of the best rythim games they ever played.