Cedric's definition of mainstream includes being appealing to Visual Basic and PHP programmers. That seems to be the backdrop of his first two points, that Ruby and Rails are too hard for these folks. I can see some of these points - folks in our reading group have been somewhat mind bent by some of the Ruby concepts, and they are Java/C# folks, which would put them higher on the food chain than VB and PHP programmers. I think that some of this is just unfamiliarity as opposed to difficulty, but there's not doubt that there is a learning curve there.
