I really like JabRef as a reference manager because of the way it works directly with bibtex files, making it work seamlessly with latex.
One thing I don't like is the standard theme on Ubuntu linux. Luckily a very small change makes it use the gtk theme by default. This is very simple but I struggled to find much written about it on the web so thought I would write it down here.
Under: Options > Preferences > Advanced
In the Look and feel section, change the class name to: com.sun.java.swing.plaf.gtk.GTKLookAndFeel
Restart JabRef and the them fits in with Ubuntu. So images below.
|Default theme (not so nice)|
|Changed the class name in preferences|
|Restart and JabRef fits in much better with the default GTK theme|