Luckily, Apple included a way to change the genie effect, but chose not to put it into a GUI tool at this time. I'm sure someone will have one written within a week, but for now, here's how you do it. Open a terminal session (the Terminal application is inside Applications/Utilities), and type one of the following:
defaults write com.apple.Dock mineffect genieThe "genie" option is normal behavior, "suck" is sort of hard to describe but it's more like a reverse twisted genie, and "scale" (my personal favorite) simply reduces the window equally from all sides while dropping it to the dock. The other nice thing about "scale" is that it's blindingly fast (on my G4/350, while the genie lags a bit), so windows vanish very quickly.
defaults write com.apple.Dock mineffect suck
defaults write com.apple.Dock mineffect scale
To activate any of these settings, you'll need to logout and login again.

