Click for full-size version. In the first shot you can see the "wave" effect in progress that occurs any time a window is unmapped; the window sort of waves and dissolves. Beryl's "Animations" plugin lets you specify animations for mapping, unmapping, focusing, and min/maxing windows. There are some nice effects too, like the "genie getting sucked into a bottle" thing that OS X has, and many others. Either these things are new or I never noticed them before.
Too many effects really does get on your nerves after a while though. For example you can set windows to "shiver" very slightly when focusing them. The little bit of feedback does help you notice when a window is being focused, and given a dense collection of windows it can help you notice WHICH window is being focused. But switching window focus is something that happens way too often, and seeing your windows shivering for the 40,000th time is liable to drive a person insane.
I'm running KDE here. My collection of Conky scripts continues to grow. I plan to upload more of them as I refine them enough that they're usable by anyone other than myself. My first thought is always "Ew, look how many instances of Ruby I'm spwaning, running all those scripts!" My second thought is that I have a dual-core processor and 2 GB of RAM. 99% of the time, my CPU is sitting there idling. I could probably set it to spawn an instance of Ruby every second without noticing any difference. Three or four every 5 minutes isn't going to kill anyone.