Not the 740, but I do have dead DiamondMax drive sitting on my desk waiting for me to RMA it. Just up and died one day. Have had several Maxtor drives though and they seem to be pretty reliable in general.
I have a 80GB D740X and a 160GB D540X. I've ran these drives to the ground and they haven't missed a beat. Performance wise my D740X with my ATA133 controller card smokes every other ATA(minus RAID setups) hard drive, even the western digital with its 8mb cache!