Replays of Vivillon, with descriptions.
http://replay.pokemonshowdown.com/ou-92240642
This one is amazing. Vivillon puts a Pokemon to sleep, takes down another, and severely weakens the final one.
http://replay.pokemonshowdown.com/ou-92246609
Not much, but it shows Vivillon decimating its fellow butterfly. #Owned.
http://replay.pokemonshowdown.com/ou-92247137
Easily takes down 2 Pokémon.
http://replay.pokemonshowdown.com/ou-92250623
Does 2/3 to Forretress, does a decent 1/3 to SpD Ninetales, and brings a Pokemon down to its Sash.
http://replay.pokemonshowdown.com/ou-92540817
Takes down a Pokemon and does 97% to Sylveon using Sleep and confusion via Hurricane.
http://replay.pokemonshowdown.com/ou-92857351
Easily takes down 2 Pokémon and would've taken down Talonflame but the guy forfeited.
http://replay.pokemonshowdown.com/ou-92864793
Does 60% to and puts Donphan to sleep, then takes down Skarmory.
http://replay.pokemonshowdown.com/ou-92992205
This one is pure ridiculous. I know the opponent wasn't the very best like no one ever was, but still. Jeez, Vivillon. Dishin' out the pain.
These replays utilize Vivillon as an attacking lead with Sleep Powder, Hurricane, Bug Buzz, and Stun Spore/Quiver Dance. It is holding the Focus Sash on all of them except for the first replay. In those replays, I could surprisingly outspeed many common Pokemon and put them to sleep, then proceed to batter them with attacks. DON'T UNDERESTIMATE VIVILLON JUST BECAUSE IT IS A BUTTERFLY. Normal butterflies can't cause hurricanes. Vivillon can, because Vivillon is the best of the butterflies when it comes to Pokemon.
Also, about the weakness to Stealth Rock, Vivillon is a lead Pokemon, and therefore its SR weakness doesn't really matter.
You guys don't realize how game-changing it is that Vivillon gets Hurricane. You essentially have a 110 STAB attack with a decent 91% accuracy and a 30% chance to induce confusion. That's the same chance Scald has to burn you. It does buttloads of damage to everything that doesn't resist it. If Vivillon didn't get Hurricane, I would not have suggested that Vivillon get an analysis. But it gets it, so don't be saying it's outclassed by Butterfree or Venomoth; if anything, it's the other way around.