BTW I found out a little bug. When there is two Emacs buffers splitted vertically and you fire up SLIME, it switches to an horizontal split. Kind of annoying. And I think it will be a good idea to be able to switch off the string animation (by customization?).
The window splitting should work better in the CVS version. I also added a new variable to disable the animation: slime-enable-startup-animation-p.
Thanx. I'll update.