It's definitely not an uncommon interpretation of the books, but I think it's generally a non-sexual attraction in those theories.
It's more like Holmes and Watson are meant to be partners, and EVERY other relationship becomes secondary to that. And because of their personalities, it means it's impossible for Watson to keep a meaningful relationship (indeed, his second wife is never even named). And they both get jealous when they get close to others (women, really).
I don't think their relationship is sexual. But asexual people can still experience romantic love, so I won't rule that out. If anything, I'm inclined to say that Holmes was an asexual in love with Watson, and Watson was a heterosexual man who fell in love with Sherlock. I think they love each other, and it's definitely platonic. The only question is if its platonic in the sense of friendship, or in the sense of romance. But I don't think the answer really makes any difference, because at the end of the day their relationship is unique to them, and the other always comes first in their minds. It's more like we're trying to figure out which relationship we lesser mortals could best understand Sherlock Holmes through.
Anyways, you all are horrible, @#%^ed up people