Thesis: Typography nerds and Farhad Manjoo don't like the second space after sentences, and think you're kind of stupid if you do. John Scalzi agrees.
Antithesis: Tom Lee dismisses much of Manjoo's argumentation and engages what's left, finding that the separation of sentences by the extra space to be a useful innovation.
My take: I come down with Lee on this one, both for functional and for aesthetic reasons. It may just be that I am old enough that I was taught that two spaces after a sentence is appropriate (however arbitrary it may or might have seemed). But as someone who spends a great deal of time in the contemplation of text, both as producer and consumer, I find it not only aesthetically more pleasing to have the extra space between sentences, which variance breaks up the units of sound and meaning on the page into more interesting and pleasing fragments in my opinion, but also more functional, in that I am able to intuitively recognize the discrete lumping of said units of sound and meaning in a better, more meaningful way without having consciously to think about it, which frees up mental resources to engage the text's meaning more fully, however fractional the increment might be.
Chip Delany taught us at Clarion that writing was a means with which to cause a series of effects in the mind of the reader, and, to me, a healthy component of that process is the rhythm inherent in grammar, punctuation, and spacing. The double space after a sentence tells me, unconsciously, to pause just a tiny quantum longer than the single space between words does, which I find both appropriate and helpful.
That said, I don't hate on people who prefer the single space, though I do find myself hating on Farhad Manjoo a little. Not for his beliefs and preferences, mind you, but because he comes across as kind of a dick in his article. Ah well, that's polemics for you.