I'd have thought I was in a larger crowd, using my Mac to blog on Blogger.com. It took me quite a while to find an OS X client. Finally did, called Ecto. Note that you need to make one quick fix otherwise you'll pull your hair out over spacing issues. Log into Blogger.com. Go to Settings => Formatting and turn off Convert Line Breaks.
Thanks to this forum post for the hint.
Note--I gave a good run at the vim-blogger integration, but couldn't get it running. If anyone does, I'd still love a vim-based solution.
In the meantime, I'm a happy Ecto customer. Much better than trying to manage posts always online and always by the web.