It comes with a very simple yet powerful GUI which is easy get used to (in fact, it'll look similar to your current post editor as well) and lets you do things like...
*. Post new content.
*. Edit/Delete the already existing ones.
*. HTML syntax highlighting and spell-checking.
*. Saves your written content automatically, so if something like an OS crash occurs... then you'd most probably get your data back.
*. Supports a lot of blogging platforms such as - Wordpress, Blogger, LiveJournal, Drupal, etc.
If you use Ubuntu 11.04 Natty Narwhal then get the .deb package from here.
For Ubuntu 10.10 users, get it from here. Once the downloading completes, simply double click on the .deb file and follow the instructions on your screen. That's it.