[anthk]

Yeah, to worse.

On Windows XP, beside the childish theme, the window buttons were very usable.

Ditto with XFCE with some xfwm4 with a round-surface squared buttons on yellow, green and red, you can find it under the last items of the list.

Let's talk about the icons and usability. On overy modern Gnome3/XP icon theme, the icons seem contrastless and very hard to see.

Meanwhile, the Tango icons are still standing a lot on the file manager's white background, with clear outlines.

[xp84]

People hate on the default blue Luna theme, but there was a perfectly professional Silver version, and the later (black with orange accents) Zune Theme was one of the most attractive UIs I ever got to use.

[anthk]

I can't find the xfwm theme, but it had a good balance between usability and "fun". That with some GTK theme such as the default for XFCE 4.6 looked fun to use without looking very childish.

Altough I must 'konfess' that the Keramik theme with the Noia icons and some handwritting font made reading advanced man pages in Konqueror a lot less "dramatic" and careless, thus, keeping the stress down.