You can change themes with Gnome quite easily and add features such as wallpaper
changers and make the panel transparent, add applets and screenlets. With the
addition of Compiz Fusion, AWN and Emerald you would hardly recognize it.
Gnome can be made to look like Vista or OS/X or you can make it look like Gnome,
which many prefer just as it is. If customizing Gnome is not your thing try
changing the desktop by installing KDE, XFCE or Enlightenment. It all depends
what your expectations are and your determination level. With Linux almost
anything is possible.