How fast is 100x CD (theoretically)? IIRC, 1x CD is 150 kbps, so 100x CDROM would sport 15,000 kbps, in other words 15 MB per second. You don't need a extraordinarily fast HD to support that.
Still, I agree. There's no real need for such a fast CD-ROM drive, and real-world performance will be far lower than the theoretical limit.