Whilst messing about adding Intellimouse scroll wheel support for the mouse driver, I made a mistake that sent the wrong codes to Qtopia. Much to my surprise, this caused a menu to pop up that let's you change the style of each app individually on the fly.
There's only two to chose from - one is the default QT style (I don't mean the default Qtopia style - this is the normal QT on the desktop style), and an OSX clone style called Hydra (that doesn't draw 100% correctly).
The other effect of selecting one of these styles is that the app immediately becomes rootless and let's you drag it's window around the screen (works on all apps, including the email app and Opera).
It's not that useful, but it's an interesting hidden feature....
(someone's now going to tell me this is common knowledge, and I've just not noticed it in the past....)