Most noticeable changes in 1.5 are Charizard's Stealth Rock ability and Olimar. Before, Olimar was annoyingly gay. Now, he's funny gay.
There's probably a more official changelist floating in someone's computer, but the readme didn't really help me much with Olimar. So...copy and paste time. Here are the most noticeable changes that I noticed when I played as Olimar.
==Olimar==
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==SMASHES==
Forward Smash - Olimar launches pikman, pikman floats longer than it should. Basically, the hitbox stays out longer. The purple pikmin fall pretty quick though.
Up Smash - What is this. I don't know. Olimar commands a pikman to jump as high as Snake's mortar launcher (Up Smash as well). Once again, the pikmen are floaty and fall SLOWLY.
Down Smash -
==SPECIALS==
Neutral Special - Airpluck is now real. No need to waste all of your time falling back to stage. BE AWARE THAT IT WILL NOT HELP YOU RECOVER. The Pikmen are going to be falling behind you, out of reach for Olimar to use them as a tether.
Side Special - Goes farther. Meh.
Up Special - On the ground, it's an ok kill move, depending on the Pikman in the lead. In the air, it's magic. Olimar has a momentum boost that propels him upward, he can legitimately recover without Pikmen if the situation is desperate. With or without Pikmen, Olimar does NOT go into a helpless state, but you cannot launch Up-B again until you land/get hit.
Down Special - ?
==OTHER==
Attributes - Obviously small. Obviously light. Bad if you suck at dodging or staying away from moves. In a match between bad players, Olimar is like a hackysack being kicked around by people who don't know how to combo.
So don't get hit. Simple answer. Your Pikmen practically move metres/feet away from you, so there's no reason to let them get close enough. Olimar's aerials seem pretty good as well, seeing that he's swinging Pikmen around that are as big as him.
I think the White Pikman can apply a flower effect onto opponents, but I don't know how I keep doing it. Up-Smash? Forward Smash? Ah well.
All in all, Olimar still gets kicked around like a beach ball, but now he can return the favour.