0.) Obviously it has to work with Blogger.
1.) Rich formatting. If nothing else I need to be able to easily create links. Full WYSIWYG editing would be great though. Don't make me do manual HTML formatting, but please don't prevent me either.
2.) Image hosting integration. I would like to be able to take either images on my local computer or off the web to include in the blog.
3.) Blogger tags/labels. I have a small blog, with about 100-150 unique viewers daily (as measure by MyBlogLog, which seems reliable.) There may be more folks who use blog reading tools, too, who knows. A decent number of the views come from people doing Google searches for "blah". These searches often lead to blog posts that I have tagged as "blah." No tagging means less visibility, so forget that.
4.) Offline mode would be nice. Really the first three thing are handled pretty well by Blogger's native web interface. But it would be nice to able to compose a post while offline.
5.) OSX. I blog on my MacBook almost exclusively and I do not want to boot Parallels just to blog. Integration with OSX spellchecker is pretty much implied too.
Does that seem like so much? I don't think so, but yet I have not found an acceptable solution for this. Seems like most desktop apps are designed for WordPress, TypePad, and Movable Type. I have tried things that are supposed to be great, like Mars Edit, and was underwhelmed. So even though nothing quite satisfies the above simple requirements, what I would really like is something that also supported:
6.) Code. I like to include code in my posts. It would be great to have something that made it easy for me to copy-n-paste code. It should escape special characters for me (like greater than and less than signs), provide code highlighting based on the language, and provide scrolling. Right now I use a PHP highlighter from Gilly. I had to hack in the CSS for this in one of my sidebar widgets. It works ok, but is a bit manual and the code often overflows.
Is there a tool like this out theere and I just don't know it? Is there a tool out there that does all of this but only with one of the other blogging platforms? If that were true, I would have to figure out how much pain would be involved with migrating... Maybe I should just build this using AIR?