One of the new features of WP 2.7 is QuickPress, a small visual editor on the dashboard.
I am using Quickpress to rattle off this post, as you can imagine it does not replace the main user interface to write content, but if you need to write a quick note for your blog, this is probably the place.
Downsides, it does not have a facility to add categories or to use custom fields, something I need to do with the theme I use.
All in all I will probably not use QuickPress to write posts, rather I will use it to quickly capture ideas as a draft post.