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Browser-based interfaces are slow, clumsy, and require you to be online just to use them. Browsers are perfect for reading web content, but not ideal for creating it. If you're serious about writing for the web, you need a desktop blog editor. If you're lucky enough to have a Mac, nothing is more powerful, or more elegant than MarsEdit.
I've used MarsEdit since version 2.x and it's always been extremely easy to use and stable.