I have a revb iMac, 8.6, 160Ram.
I use a Sony Spressa CDRW Drive and have never had any problems with it.
If you read enough posts hear, I think you will find *erratic* behavior with almost *every* peripheral discussed.
4X is the max burn speed, it seems 2X is best for audio CDR's.
Sorry this doesn't answer the Iomega question. I just wanted to pass a long a positive USB CDRW experience.
I bought the Spressa for $199 about a month ago at CompUSA. So far about 20 burns, 0 coasters.