I've never driven an Atom, but I have had the opportunity to drive the BAC Mono at length and that thing was insane. I was out of the country at the time when I drove it, but if it was available in the USA, I think I would have had a hard time not putting down my checkbook right there on the spot.
It was nothing short of amazing, and I imagine that the Atom is right there with it.
For reference, this is the BAC Mono:
