I've been looking for a decent blogging client for Mac OS X for a while now, and while I still haven't found a great one, I'm giving MarsEdit from Ranchero a try to see how well it works against dasBlog.
The biggest problem I have with this is that it doesn't support a WYSIWYG interface, just a text pad where I can enter HTML. The real question if course is if it works correctly with the BloggerAPI for dasBlog.
I still haven't found anything that works quite as well as BlogJet for Windows does. That's a great program and I really wish that it had been ported for the Mac (or that I had a smaller Windows laptop).