I do a lot of programming on my personal laptop, and the CD burner is a decent way to back up my files. Aside from that, it's pretty damn useless. Note that 650 megs of space is pretty wimpy for a backup solution anyway; you'd be better off getting a 512m flash card for a comparable-sized frequent backup of your most precious files, assuming that your new laptop's got a card reader. Those cards drop in price daily, it seems. Long and short: I think you're making a decent choice to save the fifty bucks.
Yep, I do have a desktop; it's got all my most important stuff on it, and it's got dual drives. My most important files are on both drives. I've also got some external drives.
If you save the fifty bucks and you have files that need backups, a cool thing to do is wait for a good deal on an external drive. There are some out now that function as network-attached storage-- you just plug 'em into your home network, and you can access them from anywhere. Pretty cool stuff.