Well if you do software development, why would you even look at a 12" laptop? It's sort of like asking why Apple makes a Pro desktop machine when you need to have something that you can take with you on the plane. Two different things.
In terms of one USB connection, they do have an adaptor for it. The sacrifice you make for thinner and lighter I guess.
In terms of a $200 laptop, I'll stick with something that actually works when it's not online, has a screen that doesn't suck, keyboard that doesn't suck, battery that doesn't suck, trackpad that doesn't suck, processor that doesn't suck, memory that doesn't suck, wireless that doesn't sucketc.
Pretty bold design by Apple. I think the only real thing that I'd miss would be the magnetic connector. That is handy.