The Buffy comics aren't the same status as the television show because... they're not the television show. They have reached only a fraction of the show's audience. I can assume safely that all of my readers have watched the show. I can't assume they've read the comics. In fact, I can be sure that most of them haven't. So I can't take knowledge of "The Long Way Home" for granted the way I can take knowledge of "Band Candy" for granted.
Canon is our shared knowledge. It is the structure upon which I hang my stories. It is what I do not have to explain to my readers, and what baffles me when I read stories in fandoms I know nothing about. I'm not particularly tied down by canon; I don't feel any need to write stories that stay within it. But I do want to know that my readers share it with me.
So bing, right there I've got a reason not to treat the Buffy comics as canon when I write.
As ruuger says, I might be more enthusiastic if the comics were great, or telling a great story. Instead they're kinda comic-booky, and not in that awesome literate Sandman way. The cover art is nice; the inside art is the usual letdown. The story hasn't yet won me. Eh. It might, in which case I'll pitch it to you all as something you should read. But even then, I can't assume you will.
Anyway, I'm into ruuger's conclusion: So in short: some people like the comics, some don't, Joss says they're canon but it really has nothing to do with anything unless you're writing a thesis, and could we just go back to writing fic.
And maybe I'll write some Giles/Spike to demonstrate my agreement.