I know that for my experience, it was a slight pain to get compiz working.  On top of that is the Nvidia bug that makes compiz not work so well on my computer.  Overall, my experience with it has not been too good.  Don't get me wrong, it's beautiful when it's working right.  I can see how some of these features can improve productivity by a lot since it gives you a grasp on "where" the desktop is.  I would expect the cube to be very productive when you get used to it.  Some people like scale, which is used with expose.  Some may even like the wobbly windows, but I cannot find how this can help you to be more productive.

I also like the ability to drag windows between desktop, but that's a feature that has been around since the beginning of time in Linux.  After using it for a while, on this computer and my friend's, I've decided I don't like compiz fusion enough to be using linux for it.  I find that I do not enjoy most of the eye candy after using it for a while.  I mean, I don't really focus on how beautiful the screen looks or how wobbly my window is when I move it.  When I work, I find most anything that pops up on the screen distracting.

I like the idea of having multiple desktops, but that's default within the multitude of windows manager in linux.  The only thing I really do enjoy using is the cube, it gives me orientation and allows me to switch to desktops quickly.  Other than that, I cannot imagine using it as most of the other features are too slow.  I use alt-tab a lot, with a lot of these eye candies, the alt-tab feature becomes slower.  Sometimes, I want immediate access to the window I had just lost focus of, and I want it back…now!  Not in 0.6 seconds…:)

Since I have the Nvidia bug, I cannot justify using compiz at this moment, just too many things to worry about.