After the success of our recent 'The Bicycle as a Fashion Accessory' discussion feature (!!!), what do you all think of 29" wheeled bikes?

It seems that certain parts of the bike industry, and a lot of riders (especially over the pond), are going mad for 29" wheeled bikes at the moment, but what do you lot think? They have been around for a while in various forms, but now almost every bike brand has a 'twenty niner' in their range, but is it a passing phase or are they here to stay?