The advantage of this set-up is that you could use any of a number of comfortable sub-20 pound bikes, so there's your extra 5 pounds. Plenty of folks have comfortable, all-day century bikes that weigh in less than 20 pounds...even a CF bike like a Specailized Roubaix could work, wouldn't it?...or the Pistola, which (on paper) seems to be targeted at the all-day rider.

For somebody who's a fit, enthusiastic cyclist and who has a bike that works for them on long distances, this solution is attractive because it's much cheaper than buying another purpose-built touring bike.

I'm interested in this partly 'cause I own a bike that is wonderful for all day rides (my Davidson) but not really ideal for touring. I could make it work, but it would be a bit of a hack job to fit it w/racks. The thought of having an ExtraWheel to throw in the back for short-ish tours is very attractive to me. Would love to see more accounts of folks who have used them but so far have only seen some limited tests.