I used Crossover Games from Codeweavers to install a nwn diamond edition ($10 now for the 1.69 version from Gog.com). It was fairly painless to do -- the only trick is to find the nwn directories, which will be under Library > Application Support > Crossover Games > Bottles > setup_nwn_diamond.exe > drive_c > Program Files > Gog.com. Also, the intro movies won't work, so you need to disable that in your nwn.ini file. Otherwise, it seems to be running rather smoothly for me.
I'm not that technically inclined, so this was a great solution for me. >.>