This has nothing to do with being for or against any vendor. It's alienating your users, and you never want to do that. Brands communicate emotions, it's risky to expose yourself to that. Or is that on purpose?
Apple has spent billions of dollars crafting a brand that inspires trust, quality, and modernness - and regardless of how an individual feels about Apple on a conscious level, the strong majority probably associate those three things with Apple products.
Slapping a Macbook Air in their design passively speaks to viewers by saying "we're a quality brand, you can trust us, and we're the future in this outdated industry." If you look around, you'll actually see that a lot of successful startups (usually post-first generation) piggyback off one aspect or another of established brands.
I think it has everything to do with that specific vendor (not your comment, the unpaid ad). When was the last time you saw a landing page featuring an Acer or Asus laptop?
"Brands communicate emotions, it's risky to expose yourself to that. Or is that on purpose?"
It's clearly on purpose. The (desired) communicated emotion is along the lines of "we're hip and trendy and use only the cream of the crop".
Honestly, I don't see how it alienates anyone unless you're actually against the vendor. I mean, you say you aren't but let's be real. It comes off like that's where you're coming from.
So, I have nothing against the MacBook Air (in fact, I love it, and am typing this comment on one: this is my favorite computer I have ever owned, by far); however, I know a lot of my friends do (believing Apple machines to be the anti-thesis of computers, etc.), and they are the kinds of people who might be in the market for useful software.
I guess you can say "those people are closed-minded: I don't want them using my software", but with that attitude you very rapidly realize you wouldn't want to sell to anyone (often including yourself, once you really approach the problem of avoiding closed-mindedness with an open mind ;P). To me, an abstract device would work just as well.
*This is not to excuse designers who don't test their typography under ClearType, but rather if there's a way to make my work look better naturally, I'm going to use it.
But I'm not at all convinced that an Apple laptop is less distracting than a Lenovo laptop. After all, we're discussing it in the comments, aren't we?