LKEARL  I commented earlier that D2X-XL 1.6.162 runs well on my iMac G5. Since that time I have received repeatable invalid polygon error messages at the end of level 3 where you come around a corner to see the reactor that shoots the red balls. Whether I approach from the left corner or the right corner I get the same error message. So I've changed to using D2X and it works well, but the mouse isn't as responsive as on D2X-XL. If not for this invalid polygon error, I'd keep using D2X-XL.  
(Version 1.6.170)

LKEARL  On my Mac Pro I get an error message about invalid polygons or something like that before the start screen even gets the menu text on it (it's at home and I'm at work).

On my iMac G5 it works great. What a blast to be playing Descent2 again! I need to find my CD with the Descent1 levels and see how that goes.  
(Version 1.6.162)