I’ve been using the “classic” windows theme for a while now, but yesterday I decided to switch back. Big blue title bars and task bar.
Yep. It’s ugly. But I find it more usable. There are two key features:

• The focused window is easer to differentiate. The main reason for this is that the window border get’s highlighted in the XP theme, where as it doesn’t change in the classic theme. In the classic theme, only the title bar changes.
  Of the XP themes, the blue one has the most contrast between foreground and background windows. Otherwise I would have gone with the silver.
• Bigger + Highlighting minimize/maximize/close buttons. Minor, but buttons highlighting as I roll over them seems to really keep me from missing. It’s just that slight visual indication that confirms your intention.

Actually, this was mostly inspired by my realization that Metaciy is pretty good in this department. Especially if you pick a theme that lets you adjust the color of the foreground window.