It seems to be a level of magnitude harder to find and retain people who are enthusiastic about non-apple stuff who are authoritative, can write well, reliable, and who are affordable.
We don't get review hardware from anyone (generally) and we don't have a budget to purchase stuff, so we rely on our writers reviewing their own purchases. Most of our editors and writers prefer to purchase Apple stuff, so that's what we review.
I know that there's plans in the works to get an HTC Evo 4G and I think Jacqui might review it, but while she's reviewed a ton of iPhones, she's unsure she can do an android phone justice (as she's never used one before).
On a final point, I should say that the readers of Ars and people from around the Internet seem to value what we have to say about Apple stuff. By any metric you pick, our readers are more enthusiastic about Apple stuff. Now that could just be self-selecting bias, right?
So lets see. They're saying they don't have an easy time attracting talent that can write about things that aren't apple, most of their staff prefers and buys apple equipment, the author of this article who has reviewed iphone after iphone had never _used_ an android phone before, and their readership are apple fans, and apple coverage draws more traffic.
But, of course, if anything they're biased against apple.
Ars Technica's most notable Apple reporter, John Siracusa, still holds a grudge against Apple for nearly every way in which Mac OS X went with a NeXT-style user interface over a Classic Mac OS UI paradigm.
They do a good job of producing informative articles, but you have to watch out for anything subjective, because a lot of it is quite unreasonable, and it's quite common for their conclusions about an Apple product to be invalid and useless for anyone living in the real world. The apparent bias in any given article can be all over the map, but on average, they seem to slightly prefer being unfair to Apple.
Like it or not the products sucks and runs Android.