How well does an artificial lawn work for playing?

I've read about artificial grass for years, and all the promotional materials wax rhapsodic about the environmental benefits, the ease of care ("Never mow your lawn again!"), and how uniformly attractive fake grass can look. Those are all nice things, certainly, but they don't address the primary reason to have a lawn: for play - running, walking, sitting, rolling. Lawns are meant to be used, not just viewed. So how does an artificial lawn feel?