Okay, I'm being a little unfair. Maybe a lot. But I'm amazed that after Strange Horizons has published so many stories of so many different types, there are still people expecting it to be Analog. (That's not a slam of Analog -- I don't read it regularly enough to criticize it, and there are writers I respect who have published in their pages.) Strange Horizons provides a market for many stories that would receive much less exposure, or perhaps not even be published at all, were it not for the willingness of the editors to take risks, be committed to many different types of writing, and try to stretch a few boundaries.
"Time's Swell" will seem shallow to some readers; no story has ever been published that everyone who reads it thinks is great, and different readers respond to different details. There are many beloved classics of science fiction that I think are laughably shallow, while I once knew a brilliant (though curmudgeonly) man who called my favorite American novelist, William Faulkner, a writer of "glorified pulp fiction". Being someone who likes many things that get labeled "artsy", I didn't find "Time's Swell" to be shallow, but rather thought it was an evocative mood piece, a sad study of distances. Could it have been a mainstream story if the "time ship" was taken out? Possibly. Does it matter? Not to me. An evocative story is an evocative story, and they're rare enough that I'll take them in whatever form they appear in. But a good argument could be made that this story requires the alienation the alien technology provides. The entire problem between the two main characters derives from the science fictional premise, and if a different, mundane problem was substituted, the story would not have the same resonance.
Some people have suggested that since Jed Hartman's "Future of Sex" editorial called for more SF that imagines something other than an entirely heterosexual universe, then Strange Horizons must be practicing "literary affirmative action" by publishing such (shallow) stories as "Time's Swell". Okay, sure. The same way all the prominent SF magazines are practicing literary sexism by publishing so many shallow stories that star heterosexual characters.