Well, I had a go with WLW, and I had a go with ScribeFire, and I had lots of goes with Blogger's own composer.
And after all that, even though WLW can't do as much as Blogger, it can't justify and it can't post pictures, it is still the greatest because in other ways it works so much better.
You see, I'm about to change the shape of two of my existing blogs, and that means altering or deleting many articles. WLW will be able to help me achieve this task much faster than anything else because the offline client is so much easier and quicker to use than something that runs in a browser.
What was the other thing? As I went to push the Publish button to send this article to Blogger, I remembered it. I have several Google accounts, because I use different ones for home and work - I use one Gmail account for work related activities. This causes no end of problems at home when I can end up being logged into the wrong Google account, come to post a message and find I have to log out of one account and log in to the other. WLW doesn't require me to be logged in with the right Google account because it does that automatically.
