Evidently, in earlier releases of Ubuntu, an animation add-on plugin for Compiz called Skewer could be tweaked to get a slide-in/slide-out effect for opening and closing Windows. Alas, I discovered Guake while running Quantal, and Skewer is gone from the Compiz plugin packages provided in the official repos. Guake's really nice, but the fade/expand effect just feels wrong -- is there any way to get Skewer back, or is there some other plugin that'll do what I want?
I found a great article about this in Fedora Forum:
Basically you do the following:
Launch Compiz Configuration Settings Manager (CCSM), go to the Effects section, tick the box next to Animations Add-On, then click on Animations.
In Animations; under Animation Selection; for the Open Animation tab; click on New, then:
Move this item up to the second position with the Up button, then click on the first item in the Animation Selection list (which should be a catch-all Glide 2 effect with certain exemptions), click Edit and add the exemption
Repeat this process for the Close Animation tab and you should then be all set!
Launch Guake and you should see it slide down from the Unity Panel at the top of the screen.
If like me, you find that this effect does not persist correctly over reboot and you end up with the default Burn effect (Guake appearing and disappearing in a burst of big flames) then just go back into CCSM, click on the Animations Add-On button, select Burn and set everything down to its lowest, selecting up for Fire direction. This will set the global defaults for Burn.
I hope this helps anyone. ;)