The real reason I'm using an internal hub on my bike is that that's how it came. But there's a few things I like about it over a derailleur. Since the idea is to have a portable bike, it's nice to to have the derailleur sticking out to catch on things. Also, given some of the peculiarities of my bike, the shifter is on the seat tube. That works fine since the SA hub works best when I stop pedalling, but I think it would be more awkward with a derailleur where I would have to keep the chain moving. I would probably have to move the shifter to the handlebars, which would have it's own set of problems. To me it's a cleaner look, too, and a stronger wheel, which is important when you're a little on the heavy side. My full-sized bike has a derailleur, and I like it fine, but I also really enjoy the IGH on the little bike.