Wanted to post my opinion of Luigi's MUs thus far. I posted this in the luigi skype group and most of them agreed (except for Pit).
http://prntscr.com/9a1lsp
Luigi's percent is on the left, the opponent char percent on the right. So Luigi GnW, for instance is 45 Luigi, 55 GnW, meaning Luigi loses.
Generally, characters that have good air mobility, juggle tools, and/or disjoint do well against Luigi or go even vs him I feel (with the exception of Sonic and DDD, but the mu isn't so bad for those two either). I don't think any character gets hard-countered by Luigi ,and that every character is capable of beating him with smart plays and good decision making. Lucario, I think, has the hardest time vs Luigi, but I don't find it to be unwinnable by any means. And Luigi doesn't really get hard countered by anyone either. Marth, Toon Link, and Fox are close but even those characters are doable. (Thank you PM up air and recovery).
Feel free to agree/disagree. And I will respond if I'm not too lazy (I will be most likely).