DockbarX brings much needed advancement in terms of dockbar features, ease of use, features and usabillity. This is especially noticable on netbooks where screen real estate is much better handled in DockbarX than in any other dock for Gnome desktop.
DockbarX is DockBar (a TaskBar with grouping and group manipulation) with some "experimental" features. It is not a fork of DockBar. This is just a branch of DockBar holding new "experimental" features.
The goal of this branch is to bring new and innovative features to enhance the experience of using DockBar in the long run, rather than to bring stability in terms of predictable behavior from a release to the next.
The branch do aim to be as bug free as possible, though, and to be usable for everyday computer usage (for people who are not bothered by rapid changes).
I really hope DockbarX comes to Fedora repositories as soon as possible, this dock is much better than any other on Gnome and works great. Also there are some great themes for DockbarX.
You can also look at Gnome Look page for more info on DockbarX.