Although typically I like slider, sometimes it is not practical to use because of space constraint. When a horizontal slider, for example becomes, narrow and narrower, it is difficult to get a fine tune movement.
The solution that I am still experimenting with is to use a pop-up slider. This is mostly seen in the volume applet, but, hey, let us try it somewhere else:
So by clicking on the down button (forget about the ugly pixmap), a slider will pop-up and let the user adjust the value by moving the slider handle. The slider will automagically disappear if the user clicks anywhere else, just like typical pop-up menu.
I am not really surprised if usability-wise, this kind of pop-up slider is not usable at all. However, if there is interest, I'll put the code online (it's only couple of hundred lines anyway).