If you do a lot of blogging, especially if you have several blogs and on different sites (Blogger, Wordpress), it can be a hassle switching 'identities'. I've just started to use Windows Live Writer. Once you set up all your blogs, it's a breeze to switch between them and post; it's also easy to format precisely since it's a WYSIWYG editor. And of course you can compose a post off-line. Get it here.