While I haven't the technical experience of some, I do have some direct experience. First, on the issue of the ATA66 connection, I have connected the same ROM drive to an Ultra ATA66 card, an ATA133 IDE connection, and a USB2 connection. When I rip, I get the same results on the IDE and the USB2 but I get an upper limit of 10X when I connect to the ATA66 card. Maybe the difference is that it is a PCI card but clearly it is slower with an optical drive.
Second, when I connect the same ROM drive to an IDE connection shared with a WD DMA 5 drive, I am constantly finding that the IDE connection is reverting to PIO. It is independant of whether the drives are used together; they are not. I have set everything up as DMA, turned off the computer, and come back the next day to find I was at PIO.
From here on out all my HDs will be SATA and I will keep optical drives on IDE for burning or USB2 for reading.