Iomega, the storage giant possibly best known for popularizing removable media storage with the Zip disk, has never been content to rest on its laurels.

This year marks the tenth anniversary of the Zip drive, with its (currently) 750MB removable disks. In the years following its introduction, Iomega's best-selling removable media system has been superceded by later-generation products with new features and greater capacities: first upping the Zip's capacity from 100MB to 250MB, then 750MB; later, the company's Jaz drive, with its 1GB storage capacity; and two years ago, the 35GB Rev.

But the rest of the storage market hasn't remained idle, either.

Tape -- which dominates the backup market targeted by Iomega's Zip/Jaz/Rev products -- remains a steadfast competitor, with DAT 72 in wide use in many industries. DVD media, meanwhile, has broken into the mainstream PC market, with dual-layer DVD drives now commonplace. Ultimately, 50GB Blu-Ray and 30GB HD-DVD discs may prove even more of a challenge to the Rev market than tape, which remains limited by its sequential access characteristic.

Hard drives, meanwhile, have seen an even greater transformation, with capacities growing at a staggering rate, while prices continue to plummet. Suddenly, hard drives can offer ample capacity at an attractive enough per-gigabyte cost that makes them a viable backup alternative for many home and small business PC users.

Perpendicular technology's unprecedented areal densities, lower power requirements, and simpler ease-of-installation (thanks to SATA, USB2.0 and Firewire) now means it's easier than ever for a home user to add in additional internal or external drives to an existing system.

With existing competition from DAT and DVD media coupled with the burgeoning market for hard drives themselves to serve as a back-up strategy for many users, the market for a product like Rev may never have been tougher.

Fortunately, Iomega's also not one to back down from a challenge. Witness the second-generation, 70GB Rev.

That's right: Iomega has updated the Rev product to double the capacity. Of course, this means upgrading to a new Rev drive that supports the 70GB disks. Fortunately, the drives are backward-compatible with the first-generation 35GB disks.

How does the new variation fare when it comes to performance, and how does it compete on value -- namely, cost-per-gigabyte, but also including the cost of upgrading to a new, compatible drive.