You can test and play with the blog and posts as much as you like without ever touching the live website until you're done, and you skip any security conciderations whatsoever. Well, just keep your httpd and ftpd install up-to-date I guess, or whatever way you use to push an update onto it.
The only problem I see with this right now is, like with all client-side software, it doesn't sync between multiple systems so you can't write on a single post from different locations without 3rd-party software. Still though, the advantages seem pretty big if you don't plan to write often away from home and don't want to have any trouble with software running on the site.
Read the idea on this page: http://laktek.com/2012/04/19/punch-a-fun-and-easy-way-to-build-modern-websites/
(first 2 paragraphs).