I'd played around with MarsEdit back when it first came out. I liked it, but couldn't justify using a client application when the Wordpress posting interface works very well. I see that Josh is trying MarsEdit so I thought I'd give it another go.
It does provide a handy way to manage multiple weblogs, and I have it configured so I can easily post to the PachyBlog as well.
UPDATE: It looks like WordPress 1.5 has fixed the issues with the XMLRPC interface, since MarsEdit is able to communicate with my weblog just fine, without requiring the xmlrpc hack I had to use before. I also just posted to the PachyBlog - something I hadn't done since September (oops). MarsEdit just makes it so easy (don't have to remember passwords - the KeyChain remembers all...)
UPDATE: Looks like the update post function is a bit borked. It didn't want to update at all... I ended up deleting and recreating this post to update it. That won't do... It would also be handy if MarsEdit understood hierarchical categories like WordPress does, rather than providing a flattened list of keywords (wait - that's a folksonomy :-) - see - hierarchies DO have their place...)
UPDATE: Hmm... Updates seem to kick the post into "Draft" status... Still on the blog, but invisible... I've filed a bug with Ranchero.
but it looks like it got deleted or lost almost immediately. Doh. I've also filed a bug in the WordPress Mantis database just in case it's something funky in their xml-rpc implementation.