In that past I've created custom live unix distro CDs for myself and although it worked I found that it was so time consuming and generally such a pain in the bum that it just wasn't worth it. Yesterday I had the need (that nerd need, not because I had to, but because I wanted to) to create a customised CD for the house1. I'd heard good things about RemasterSys and figured now was the time to try it.
Holy crap it's awesome. Customise your setup as you want it, make sure you do the necessary system wide alterations (/etc/skel, and so on) and then just fire and forget. A few minutes later you either have an ISO or the CDFS ready to be altered before you turn it into an ISO. I didn't have to worry about clearing down rubbish, then mashing it all into squashfs. It Just Worked.
If you need to create a custom Debian based live CD quickly, then I encourage you to look at RemasterSys. It's quick and works like a dream.
 We have an old laptop with a mostly dead hard disk, and it's been running an Ubuntu live CD for months. Sadly it means that everytime you shut it down certain things need to be reinstalled, such as Flash support. No longer is this an issue thanks to Redcatch Linux Five Thousand.