GTK Theme on Non-Native GTK Apps
I just found out that my Murrina Y Blue theme breaks big time on OpenOffice.org. As you can see from the screenshot below, the menu padding looks perfect on Nautilus but hideous on OOo. The combo box in the OOo toolbar also looks ugly. The button is much larger compared to the text entry field. I don’t know if I can fix this thing since OOo is not a native GTK application.
I think OpenOffice is the most out-of-place looking application in my Gnome desktop. The fonts are always different, the icon theme is ugly (but I heard they finally Tangoify OOo at Fiesty) and the interface sucks.
Firefox is not a native GTK+ app too but it integrates much better with the whole desktop (I do have some complaints though). So far the best non-native-GTK+ app that pleases my eye the most is the Eclipse IDE! I think all Java desktop apps should use whatever Eclipse developers are using (seriously).
solaris 
SWT? Same framework used by Azureus. It looks good but rumour has it that it can (could?) cause headaches for the programmers too.
@Ronny:
Yeah the same one as Azureus. It has that distinctive curvy tabs :). Too bad if its too hard to develop with, it looks really-really nice (on Gnome at least..). I’m have JMeter here at work and the UI looks archaic.
Stupid curvy tabs… PORCENTOARROBA!