I’m writing this in Windows Live Writer. It’s pretty incredible—setup was easy, and there’s a mode for editing the entry such that it looks exactly as it will look after it’s posted (i.e., with the right font, layout, etc.), though without all the page adornments (header graphic, sidebars, etc.). There is a preview mode for that though—if you could edit in the preview mode, now that would be incredible (better still, if you could edit the page directly, inline, presuming you had the appropriate credentials—a truly writable web!).
It’s too bad this is Windows only—I have a Windows box in my office, but it’s a desktop machine, so I don’t have it when I travel (I wonder if it will run under Wine?). I’d also love to see this integrated with Firefox, something like Performancing, where you can select some text, then right click “Blog This”. There is an IE toolbar, but that doesn’t help me.
In addition to being a nice tool, this does give a glimpse into Microsoft’s strategy for the web: Desktop/thick client apps as an extension to web/thin client apps, providing all the advantages of web apps but better UI, better performance, and offline support. So far, I like what I see.