In the new beta (2.06b) I am having issues getting sketches to run fullscreen presentation mode in OSX Lion when using a projector/dual screen.  It works fine on the computer by itself, but when I set up to a projector and do "mirror displays" the sketch wont appear on the screen if you start it in presentation mode.  It just stays grey or appears to not come up at all (though the Java icon does appear in the running apps list).  If you do an extended display, it works fine -- it opens up full screen in the secondary monitor/projector by default and works great.  But I can't do mirror displays in presentation mode it seems.