I haven't found speed to affect burning.  However, TransMac (with good images) tends to be very effective (via Windows).  That's not always true.  I've had really weird burn failures also; I've never been able to systematically track why.

I think the Toast option mentioned may only be relevant to pre-10.5; and if you have a modern Mac with 10.4 or below that'll probably be a flawless method (I don't think I've had problems using the Superdrive on my G4).