Here's a tweet from the author of the article before it was published that might shed some light on that:

"I have possibly the nerdiest, longest article I've ever written going up at 1930 Central tonight."

https://twitter.com/DrPizza/status/260154952868057088

So, I'd say the audience is nerds in general. I agree the article doesn't seem to have a definite target audience, but I think — in some sense — that is the beauty of Ars Technica's content. It's accessible enough that non-technical nerds can get value from it, but technical enough that more hardcore nerds appreciate it.