I use nanners well, and they definitely have a place in my Diddy game...
however...
the problem with nanners is that a good, balanced player, regardless of whether they are using Diddy or not, will be able to either turn your nanners against you, or if the two of you are both equal in nanner skills, will at least be able to use them well enough to negate the huge advantage that nanners are supposed to give you.
For instance, when I play Diddy-mains, they usually give up on pulling nanners because every time they do, I take control of their nanners and within seconds, anyone passing by would think that the nanners were mine... except for the fact that I'm playing as Fox, Kirby, Olimar or someone else that isn't Diddy lol.
P.S. beware of pulling two nanners out if your opponent is playing as IC; picture both of your nanners being turned on you at the same time lol.