I've attempted it. I use Panic's Prompt to SSH back into one of my machines and program from there. I do not have an external keyboard for the iPad, but using the on-screen keyboard is just a pain. You have to think how you are going to be switching between the different on-screen keyboards to find very frequent used keys like brackets, parens, semicolon, etc. This works in a pinch but not for long periods of time.

With having an external keyboard it's another pain to reach up and touch your screen to switch apps. Just stick with a laptop, you will thank yourself in the end.