Diddy Kong has been in the series since Brawl, but it was only until now that I started to like him a lot as a character. I think Donkey Kong's nephew certainly got upgraded this time around.
He's a small character, a lot like Pichu, but after this recent update, he's got a lot of power to his moves. Someone that small, short, and powerful is a force to reckon with. One of his least useful moves is tossing a banana peel for someone to fall on.
And he has a pretty good recovery. I will say those rocket barrels are far better for causing damage than saving yourself from a fall. I had a few deaths by accidentally piloting them toward the bottom of a pit or the edge of a screen.
His final smash has him using a super rocketbarrell jetpack and causing damage all over the screen. One unlucky opponent gets hit the hardest at the end. I liked it as a final smash but it is pretty hard for your foes to dodge.
When Kirby takes Diddy Kong's power, he gets a cute red hat and a peanut gun. The peanut gun for both of them is a decent power. It doesn't cause a lot of damage, but it's can cause many of your opponents to retreat and think of a different strategy. Typically giving yourself the advantage if you can counter them faster.
Online I did really well with Diddy Kong, though some people managed to best me with him. Hopefully any recent updates really won't change his stats. He's perfect right where he's at, in my opinion.