So to state my question more clearly, can I use WLW without also having to interact with any other Windows Live products?

Also, is there any reason you would recommend it other than that I'm on Windows 7? From the screenshots, it's got that "ribbon" interface which I actively dislike.

Re Windows Live Writer: is this a standalone application, or is it part of some Windows Live "service" that I would need to subscribe to or something?

In terms of crossposting, I mean that I presently have a personal blog and am considering additionally contributing to a multi-authored blog, and occasionally crossposting the same article to both blogs.

I'm aware that there are issues with search engines and duplicate content, and am separately trying to figure out a good solution for this. (There seems to be a rel=canonical tag that looks promising..?) But I don't want the choice of blog editor to make this decision for me - just trying to keep my options open here.

I'm looking for something that will support crossposting.

I'm not clear by what you mean by cross-posting. I am clear on the fact that WordPress.com does not provide tools that can be used to create duplicate content blogs. Please read > types of blogs allowed and not allowed http://wordpress.com/types-of-blogs/
Also note how Google views duplicating content across domains and that their Panda algorithm will detect duplication > http://support.google.com/webmasters/bin/answer.py?hl=en&answer=66359

I use Windows 7

See here please: http://en.support.wordpress.com/xml-rpc/windows-live-writer/
See also http://en.support.wordpress.com/xml-rpc/

So, I thought if I described some relevant characteristics about how I blog now to you friendly folks, you might have some recommendations for me:

- I use the HTML editor almost exclusively. I use basic markup frequently: strong, em, blockquote, strike. I let the HTML editor magically insert the paragraph and list element markup for me & really appreciate that.

- On the rare occasions that I use media, I usually rely on the "Upload/Insert" helpers. I switch to a visual editor only for placement of images or other media, and may then switch back to HTML for further tweaking. I use the "more" button to insert that directive because I can never quite remember how to spell its syntax.

- I use categories and tags. I schedule posts for later publication.

- I use both standard and aside formats. I don't use gallery format.

- I frequently preview to read through what I've written and then go back to the editor tab to revise.

- I'm looking for something that will support crossposting.

- I presently blog only at wordpress.com.

- I'm not interested in ads or making money with my blog.

- I don't do much social media. I'll likely do Twitter someday.

- I write lengthy comments. (I have no idea if blog editors are used for comments too.)

- I use Windows 7. I don't use any Windows Live programs, don't use Microsoft Office (I use OpenOffice instead), and dislike its l"ribbonized" ook&feel.

Thanks for any suggestions!

Victoria