I use a Spongy Wonder seat. The Spongy Wonder is designed to only contact the sits bones. You are right about to be concerned about balance. When switching from a nose to a nose-less seat the transition is jarring. It takes a little while to compensate for the new saddle and shift in center of gravity. I was back to full confidence in riding the bike within an hour.

For someone learning to ride I imagine it wouldn't be any harder to learn than a saddle with a nose.

The other thing about the Spongy Wonder is that it helps with getting back on a bike if you have any pains or issues in the mid-line since there is no pressure there like a traditional seat.