From what I understand (and this is a bit tenuous), holographic storage currently sits between tape archives and online hard disk systems. It's far more reliable and smaller than a hard disk, but accesses much faster than tape.
If I recall correctly, these folks are expecting to catch up with hard drives on the cost per gigabyte front in less than ten years. I would suggest that this means that they're going for near-line storage, where ATA disks are now making inroads.