Having used Poser 8 on Lion since day one, I haven't really run into any problems I can't overcome.  The obvious problems I have run into are the above mentioned library glitch (though the library is still workable, problems with the eyedropper, and occasional rare onetime glitches which seem to have decreased with time (an occasional saved work copy).  Alll in all, I don't find that it has messed up my workflow and all of my scripts seem to work fine.  rendering speed seems to be the same or faster, Carrara and Poser seem to working fine, Bryce is, well, Bryce... I haven't opened Hexagon yet.