Scrivener is a super-slick app for writing. It makes it easy to organize and draft your work. Very nice.
Although it seems a little harder to use than Scrivener, Celtx is a free, cross-platform app that is arguably intended for an even more professional group of users.
A note if you migrate- all of your work in each Scrivener file are RTF documents in a series of folders within the folder that makes up the Scrivener 'file'. Scrivener was on the fence between good and bad scores. It was painful but the format was open.
How Good is the Linux App?
App name should be marketable
Has a nice app icon
Uses Tango icon guidelines
Slick UI that's fun to use
Killer feature people talk about
Top-level domain name
Site has FAQs for users
Site has a User forum
Site has a way to contact the developers
Packages for Ubuntu, Fedora, and openSUSE