I bought a run-out 1GHz eMac with a CD-ROM for a bargain price and swapped the CD-ROM with a Pioneer 107 (equivalent of the new 8x superdrives). Bye bye warranty, but welcome superdrive goodness.
I must say it really depends on what you do - I use DVD burning all the time, for making DVD videos (home and for projects), for archiving music and documents and even for transporting large files (especially DV files, even though this is more effective by firewire, sometimes other people don't have firewire). So I am loving the superdrive.
On the flipside, if you do none of the above, I can understand that you would probably find it of no use whatever. To each their own, it's something you need to consider before you buy.