Definitely has my favorite level designer out of all the games in the series, in spite of some of the prop objects not being very useful overall and taking up way too much space on the map. SSBU and SSBM might be better, but I love building levels so very much and probably made a couple hundred in this game. Also, Subspace Emissary was great.

Pros -- Almost everything.
Cons -- Occasional slipping, people acting like they're the most hardcore gamers ever while blaming their shortcomings on slipping.