Honestly I haven't. I didn't use Olimar that often either. Most people I happen to face online use Sheik, Toon Link, Luigi, Fox, and Sonic. Came across a couple of Ganons and Marios as well.
You have no idea how annoying Olimars are... I find them even more annoying than MKs, to be honest. Etremely small (if not smallest character), very floaty (super easy to get back to the stage), possibly best projectile that's hard to dodge (them all) and they latch on to you for even more damage racking.
Having them latched on to you blocks your attacks and/or delays them.
By using the whistle he can block ANY attack with them.
They're freakishly strong, and come out in an instant.
His grab range is ridiculously long AND fast with almost no cool down if he misses.
Not to mention it's ridiculous how one tiny Pikmin can completely block a full charged shot from Samus,w hen in reality it should tear them apart like balloons. >_<
He really is a headache, lol. He's one of the 3 characters I want balanced out the most. (As well as Diddy and MK)
EDIT
BTW, this is the best thing that could happen to Olimar, IMO. >
Samus taking 3 of his Pikmin out with a SINGLE JAB! TvT