Barbara Dybwad's post on the Performancing Firefox extension, provoked me to give it a whirl. Performancing embeds a weblog editing tool directly within Firefox. I'm using it to create this very post.
Performancing isn't going to push me off of MarsEdit on the home Mac. However, it might be an upgrade for me on Windows, where I haven't found a satisfactory weblog editor. It's a little inefficient in terms of screen real estate, and I'm sure there are some glitches under power use, but it has to be better than editing within an HTML form.