I haven't really felt the need for a separate tool to write blog posts - doing it in the browser seems to work well enough, especially with the real-time spell check in Firefox. But I can't resist trying out new free software :-)
I added this screen shot to test inserting images. That's one area where Blogger can be a bit awkward.
[screenshot removed to allow publishing]
It also looks like you can add tables which I don't think Blogger allows (unless you edit the HTML directly).
Humorously, Live Writer shows "Firefox" as a spelling mistake. (but "Blogger" is ok)
So much for images. When I tried to publish it said "the weblog does not support image publishing". Blogger certainly allows images, so I would interpret that to mean that Live Writer's interface to Blogger doesn't handle images. It did offer to let me configure an FTP site but I wonder how "user friendly" that is for most people. I assume if you use Microsoft Live Spaces for your blog then you can publish images.