Well, I'm going to a smashfest tonight, so maybe I'll use it to brush up on Marth. ; )
In the meantime, I'd like to ask some questions.
Is Marth's fair faster?
If so, I think our aerial game as far as spacing won't be so easy. It's like Peach's fair versus Wolf's bair. She has more range, but it's slower. Now, our bair isn't slow, but if Marth's fair is faster by a pretty good margin, the game is no longer spacing, it's using your move before your opponent does. With that in mind, even if the moves are nearly equal in speed, Wolf doesn't have such a great margin of range on it. This means that it's a game of predicting the user of the first move and punishing with yours.
I've found that rushing into a Marth is pretty stupid, because your moves are similar, his being, probably faster. He can use two fairs in one short hop (but his falling speed is different, which is why I asked).
Be sure to predict the Marth, and know that he can sneak a fair into a bair assault and ruin a potential chain (confirm?).
Other than that, we also have a projectile. Keep that in mind. Also, someone should figure out if his fair eats our laser. I would assume it doesn't, but who the hell knows.
Note the CG everyone mentioned. Avoid it and use damage from Marth in the beginning so he doesn't get that free damage. In fact, if someone would be as so kind, figure out the specifics of the CG. Or if you already know, please do tell.
Offstage game. There is no offstage game. Stay on the stage. Marth's fair is beast for saying "i'm fast, gtfo" and slapping you if you try to gimp him. If I were you, I'd try and laser him (because I'm an idiot), offstage, and then grab and edge hog him. I think if you don't have enough time to get off and on to time the edgehog well, you can lightstep and immediately flash again to grab the ledge. Not confirmed, so I'll see if it's possible later today. Generally, you tend not to try and gimp Marth, because that UpB is pretty ghey, but if you time it, the prince will fall to Hell.
Shine is win in this MU. It tells Marth and his fair to gtfo.
Jumpshine to bair is combo. Yes? No? Not sure if that was confirmed.
This MU is clearly 50.5:49.5
EDIT: Oh, DI those dancing blades. What is best punish? Will fsmash reach, or is laser the best bet?