I'm not afraid to admit it: I'm a fan of Gnome. I think KDE looks to cartoonish. I actually prefer using OpenBox with a slew of lightweight apps for window manager addons, but that because too much to maintain, and I have better things to do with my time.
It's hard to find a nice, clean set of decorations for Gnome that mesh well together. GDM theme, icons, wallpapers, GTK themes, etc that all blend well together to create a complete, polished look.
Recently I found the "Colors" theme set on Gnome Look.
GDM and Wallpapers: http://www.gnome-look.org/content/show.php/Arc-Colors+GDM-Walls?content=88305
GTK: http://www.gnome-look.org/content/show.php/Shiki-Colors?content=86717
Icons: http://www.gnome-look.org/content/show.php/GNOME-colors?content=82562
Nice and simple.