From electricmotorcycleforum.com

I was lucky enough to get to ride the Zero S at the Semper Ride event in San Diego. When I sat on the bike it felt a lot like the X. It definitely rides different. It accelerates like a stock X without the perm motor but has a much better top end. I hit 58 mph easily. This will make a great commuter bike. My X has the perm motor so its much quicker due to the lighter weight and bigger sprocket but the S will walk away from it after it catches up.