Mourning the loss of two spaces. (& blog pause)
But for my own writing, it's become too annoying to switch back and forth from two (manuscripts, emails) to one (web work, e-newsletter). So I give up.
I will now be training myself to use one, lonely space after terminal punctuation. It's the end of an era for me. (sniff)
Although I'm switching so I can lessen my own writing frustration, whether you should do the same is up to you. I've judged many writing contests and never penalize entrants for spacing choices, as long as they're consistent about them. My agent uses two spaces, and a quick check of recent correspondence with editors shows that seven of those eleven New York editors also use two--so while there may be a trend toward using one space in publishing, it's hardly universal.
Bottom line: if a publisher specifies a preference about spaces between sentences, follow it when you submit there. Otherwise, no one much cares. Honest.
Now that Write Now Quotes is rolling (10 issues so far and going strong), I doubt I'll be posting here much. (Not, LOL, that this will be much of a change.) So if you'd like to hear consistent suggestions and advice from me, please join the free WNQ newsletter. I look forward to seeing you there!