I've been using Windows Live Writer Beta for some time now and I have to say that I'm pretty impressed with it. Live Writer works flawlessly with Subtext, and that said alone speaks volumes for me.
Back when I was using Dasblog, I used w.blogger, which is a nice piece of software, but it didn't have the flexibility I needed, plus it did not always format my postings properly in Dasblog (which incidentally, could be related to the specific version of Dasblog I was using at the time - since then, a new version of Dasblog has been released).
Windows Live Writer also has a handful of really cool plugins, such as the ability to insert snipped images on the fly, not to mention the ability to insert Windows Live Maps directly into my postings.
Speaking of Subtext, the new version is keeping the comment spam at bay, a definite plus -- big time plus. I am also appreciative of the fast performance it offers (gotta thank the Microsoft SQL Server backend for that).