I’m not just a bike nerd – I’m a Rivendell bike nerd. Grant Petersen, the owner of Rivendell, just put up a blog post that could be called “in defense of double top tubes.”
Some people like the second top tube, some people hate it. Some people could go either way. I’ve been looking at them for a while, thinking it would be a great place to put a frame bag. I made a little mock-up, and I’d say that the idea of a nice bag between the two tubes makes me like the extra “undertube” a lot more.