Link does seem a bit OP to me due to his combination of decent weight, great Smash power with his sword, and the ability to switch from powerful melee (regular and Smash attacks) to ranged Special attacks.
I don't think Link's OP at all -- rather he's finally competitive. After a long history of being not very good at all, Link is finally a contender.
Whether or not someone is OP probably differs at different levels of play, though.
I like Zero Suit Samus mainly because of her mobility, ability to stun and her side special is still great. The addition of the rocket heels also makes her Smashes a lot more solid and creates satisfying explosions whenever you land a good hit. Her down special also has a lot more utility now, as it's both a potent attack and evasion move.
As time goes on my proportion of playing as her, especially for long stretches, only increases. She's just that good, and as a fan of her from her first appearance I'm naturally quite happy. When I take a break from her it's usually as Zelda (who is fun to teleport around as) or Ike. I can't remember the last time I played anyone else, come to think of it, which has me thinking I need to branch out again. I do like Link...
This one guy I fought online in 4-way For Fun beat us all like 5 times in a row as Sonic, which was quite a surprise. Sonic, succeeding at something post-90s? As a long-time (and arguably lapsed) Sonic fan, I welcomed it.
I am a bit miffed that her up special is just a rocket kick and not a upwards plasma lasso, though, because it reduces her recovery a bit- I'll try and lasso upwards after falling but instead just jump up a bit and miss the platform due to misjudging my distances. It is a bit more powerful, though.
No way, that's my favorite move!
Hitting someone with it just right is so incredibly satisfying and the highlight of my experience. I also use her flip jump like a boss. I love hitting people with it when they least expect it, either by attacking someone who's otherwise busy or by jumping over someone who's facing me and hitting them from behind. I love both these moves because they're not just powerful, you feel like a super-skill boss when you nail them.
And hey, speaking of differences between versions, I added my first friend that I met randomly playing online.