For me, it seems to be safer than biking. I had one fall in two years and ~2500 miles of riding, and usually I find that if you hit something, you start naturally running before you even notice you're off your board. I used to have a bad bike crash about once a year, and have been pleasantly surprised so far on the boosted.
I've actually lost balance a couple times while on my board going around 20 and at those speeds I've been lucky to just kind of sprint off the board still standing. It's definitely an art though, I don't think it's always possible, especially at higher speeds
