Single speed is fine since you most likely won't use the lower gears anyway.
Just be sure to use a single-speed frame or you'll have to get a chain tensioner. That leads to problems (more parts = more problems).
I always thought this would make a great E-bike. The frame and forks are all chromoly, and it's a single-speed frame. It would be fast.
http://www.bikesdirect.com/products/dawes/deadeye.htm
