I've also tried out Reunion. While you are totally right about it being very resource efficient, I found the user interface lacking. The feature set seems great, but the user interface looks like it came straight from the 90s. If you do not care that much about charts or the user experience, Reunion is worth a look and they seem to have a great reputation in the Mac market.
But since " daciodan" (is he an admin on this board?) thinks we're "FamilyTreeMaker losers" we should discontinue the discussions of alternatives for us "FamilyTreeMaker losers"...