This is exactly why I run focus sash. If you get outsped on turn one, you can get the sleep powder off and get at least one more chance to do something. If the opponent doesn't have any priority, you can quiver dance and hit back in the guaranteed sleep turn, and after a quiver dance, you have a very good chance to 2HKO a lot of things. If you predict a switch you can at least get off a hurricane.The only thing that really counters Vivillon is anything that is faster than it on turn 1. Which sadly is lots of things. I only use it nowadays if I'm positive I can outspeed the opponent's lead.
A perfect example is mega Charizard Y. With any item other than a focus sash you get outsped and OHKOd. (ok, there is choice scarf...) With focus sash, charizard is asleep, you get a free quiver dance AND attack, and a very good chance to KO with a second hit (has happened on battle spot many times, but I suspect there is less priority and switching in that metagame).
Sucker punch priority is useless too since you