Short Intro: I've been a Zero owner/rider for 6 years, and until recently generally happy with the bike.
But imagine: You are riding your Zero home after a dinner with friends. It's dark and you are in the middle lane of a busy freeway. Suddenly your motor just ... stops. Your bike slows down rapidly as cars and trucks whiz past you. The bike stops, dead, in the middle of the freeway. An 18-wheeler narrowly misses you and honks his horn. The only thing you can do is run the bike off to the side of the road on foot, dodging traffic in the dark.
This was my experience the other night. And it's not the first time. I have been experiencing these random cutouts now for two years. I've had the bike in service twice to fix it, at a cost of $2000, and they have not been able to fix it. They say the best they can do is try again for another $2000. I contacted the manufacturer and they won't even return my emails (I've tried 4 times in the past 4 months and only got one reply asking me to verify my serial number). I even contacted their Director of Customer Experience directly and he didn't care.
The bike is great - quiet, efficient, easy to drive. But ultimately you have to also consider the company you are buying from. Do they stand by their products? Will they be there to support you when you need them?