I've used them quite frequently, with pretty good success.
Here's a case. I often record at a friend's house. After we have had a session, I'll dump the multi-track file to a CD-RW, bring it home with me where I can play around and do some mixing of the recordings (add effects, change volumes, etc). Then I save the changes back to the CD-RW and bring it back to my friend's the following week for additional recording, patching, etc.
You can also write to CD-RW's as if they were a CD-R. This works OK if you just want to backup a single file. However, if you want to read/write to them like a hard drive, you will need packet writing software. I use Direct CD from Roxio (which some people feel was actually invented by Satin).
BTW, gilwe is correct, for the most part you can only read CD-RW's in a CD burner.
Now with all of that out of the way, what exactly is your question?