Currently Discussing: Ness
Oh, hey lookie there. Heh... heh...
OKAY!
So Ness. He's one of my "secondaries." I'll have to admit, while he does have some wildly different aspects compared to Peach, choosing him mainly to deal with match-ups won't get you far. As has been said, the high tiers are as much as a hassle as usual - with the exception of Falco.
What you do with Ness as a secondary is counterpicking him against
playstyles. His magnet shuts down
a lot of spam. Not by absorbing everything, but by simply having the magnet - campers like Lucario, Pit, Fox, Falco, etc. - all instantly slow down on the B button. Camping being something that can annoy a Peach to no end, Ness is a potential instant fix.
Another good point to having Ness on the back-burner is his amazing KO ability. If you're finding it harder than usual to KO an opponent, Ness and his bthrow is a godsend. Choose him against those opponents you ****, but
just can't get a final fair on.
Learning him... I think will vary. I've used him lightly since 64, so the workings of PKT aren't to much trouble for me. But overall, I don't see a noobie having much trouble beyond that. Both Peach and Ness excel in the air, so the bread and butter won't be too hard to get down. The recovery, the higher jumps, and the projectiles will take some time to "master" though.
In the end, Ness would be something good to have - nothing to rely on. I'd give him a 2.5/5.