The Zip is based on floppy disk technology, while the Jaz is based on hard disk technology. Jaz carts should last a long time as long as they don't have a head crash (unlikely).

http://en.wikipedia.org/wiki/Iomega_Jaz_drive

So yes, I think they are work keeping as backups, especially if you have a drive or two already and good media. You can also pick them up on ebay cheap from time to time so there is no major money investment involved.

For backing up old 68K machines, 1GB is HUGE!