I have (like quite a few others) found the 1008im to be rather unreliable at 8x anyway. Even if my drive recognises a disk as 8x, I never select higher than 6x. Because of the way speeds step up during the burn, I find 6x takes about 10 mins, and 4x takes about 13 mins.
Incidentally, I find that when burning at 8x, it takes almost exactly the same time as at 6x (a strong indication that it struggles at 8x).
Overall, I have found if you stick to 4x, the burns are very reliable across a wide range of media (only getting the odd failure now and then). If you use 6x, the rate of failures increase somewhat and the requirement to re-burn offsets the minimal time benefit.