Beryl...
1) You see a video or screen shot and your eyes pop.
2) You proceed to install it.
3) You manage to get it running and you go "yay" and "this is way cooller than sliced bread".
4) Your non-geeky mate(s) notice it when their over and go WOW WHATS THAT? How can I get that on my computer?
5) You sigh, and explain the situation to them.
6) A day or two passes and you notice that your not using it so much.
7) You realise that its just pure eye-candy with very limited benifical/functional features.
8) You proceed to quite innocently change a setting to see if it will reinvigorate your interest in it using beryl-manager but somthing breaks without warning when your apply the changes; your system crashes and KDE will no longer start up the next time you login.
9) You spend some time trolling the net looking for a fix; your glad you installed fluxbox so that you can at least gain access to Firefox and thus search for a solution to the problem.
10) You get lucky and find a forum post on some obsucre and alien forum that will fix the problem - You feel like a linux guru. (Then if you were me you would proceed to screw your file/folder permissions up, then you feel like a even more of a n00b then when you started using linux

).
11) You can no longer be arsed with it and think, yeah its nice but ultimately what is the point?
What I am trying to get through here is
my experience with it. Yes it is very cool to look at and use, but really the novelty quickly wares off. After 3 or 4 days I couldn't be bothered with it.
Off the top of my head I can only think of two features that are of real use to me. 1) It is nice not seeing an echo of the window as you drag it around the desktop as is the case with a 2D rendered desktop. 2) Folding the corder of a window that is expanded can be useful if you need to see what is in the window behind i.e compareing information in two documents where one document window is behind another. It means you don't have to minimize windows. But even this is only useful if the window you want to look at is immediately behind the currently active one.
Depsite what I have said here and I may appear to be contridictive now, it is worth taking a look at if only to satisfy your curiosity. Just don't be suprised if you find your self thinking what all the fuss with it is about.
As for installation, you might be better off with a Live-CD such as
Knoppix 5.1 if thats all you want to do is see what beryl is like. Would save all the fuss of installing somthing that (going on your post) you don't use too often.