When I have spoken with Iomega technical support, they told me I don't need Iomegaware with OS X. In my experience, Zip disks work fine with the generic USB drivers built into OS X. Although, I wonder if OS X drivers offer the same verification option that Iomegaware does. Even if it doesn't, at least you won't have to deal with Iomegaware crashes & data loss as Mac OS updates come out.

If you format a Zip disk in OS 9 with Iomegaware, it installs drivers on the disk (the driver version is shown via Get Info on the disk). If you format the same disk in OS X with Iomegaware, no drivers are installed in the disk (Get Info under both OS 9 & OS X show no drivers). I brought this discrepancy to Iomega tech support, speaking with several technicians. It was very clear they have no idea why this is the case, and emphasized that Iomegaware was unnecessary.