I didn't see bikegonewild's favorite -- Pi in San Francisco -- but I tried out a BionX equipped Specialized and one of the UltraMotor A2B e-bikes. There's some question on whether these powered devices are "bikes" or not, but there's absolutely no question that these are tons of fun. Here's Annie Fike of The Bike Rack in Washington DC trying a BionX equipped bike. Her shop serves the messenger and urban cyclists in DC, and even she thinks these machines are fun.
Tim Grahl and I talked about electric bikes, and we decided we'll cover them in a series of articles over at Commute By Bike in the coming weeks. We'll profile some of the products that he and I think are interesting and we'll talk about how bike retailers are responding to (or resisting) this growing market.