I've tried several OS X blogging tools, but none of them compared to Windows Live Writer. This post, however, was authored in Ecto 3 beta from infinite-sushi.com, and it comes close to WLW. It even supports OS X services! The link to the "alpha" version in the news blog actually downloads the beta version, I'm on 3.0b2.
I'll have more to say on Ecto as I test it, but it's great to see this emerging.