On mine with 10.5 and 10.7 if I do a restart with saved oc settings the card will freeze on bootup but rest of the system will still be fine... also with those same two drivers in World of Warcraft there's loads of artifacting left and right and every now and then all character models will disappear leaving on the detailed things behind like shoulders, weapons and whatnot. On 10.6 I don't have this issue, don't have it with 10.4 either but there's an obvious image quality difference between the two.