Also if you do use Logic 6 on OS X. you will have have no VST support at all!!!!!No Waves, no Altiverb etc...
Both Altiverb and Waves will be supported in audio-unit format and thus will work in OS X with Logic. Altiverb is scheduled for next month. I don't know the schedule for Waves, but have seen a press release that they are committed to support this format.
Audio-units is a new plug-in format in OS X that is more capable than VST. Emagic has taken the position to only support audio-units in OS X to enhance that format's chances for success. They still support VST in OS 9 so that as the migration to audio-units happens people can maintain compatibility with existing plug-ins.
You can read more about OS X and audio units from Emagic here:
http://www.emagic.de/support/osx/index.php?lang=EN