GNOME
At home I just use KDE - but there is no KDE on the Sun-Solaris :-( .
Love
GVim
The only Gtk+/GNOME application I like. But then for Vim GNOME is only one of many supported GUI's.
Hate
Creating distributions
Just read Why I hate Gtk+/GNOME from the Ada programming blog.
GEDIT
What an pathetic editor - Only Notepad is more primitive.
Pango and Cairo
Sesitive Bitches where the smalles problem mean all you gnome applications become unreadable. Don't dare forget to setup your font cache!