From what I played of Sm4sh on a 3DSXL, I don't mind it too much, although naturally holding a relatively "sharp" and thin console for long-term Sm4shing does get a bit uncomfortable. I should totally rig up a grip for my 3DSXL with handles shaped like a GCN controller; I bet I'd feel more at home. 
Hmm, the Five Below near me does sometimes stock shoddy aftermarket GCN controllers...
Hmm, the Five Below near me does sometimes stock shoddy aftermarket GCN controllers...