Just got my iTouch and of course quickly found out how limited it was in terms of stuff to do with it-- until I "discovered" jailbreaking.

Since then it has been a daily joy to discover the things this wee beastie can do. Basically, owners of iPhones/iPods/etc. are walking around with Unix boxes in their hands, they just usually don't know it. After discovering that FreeBSD was what was under the interface, I knew I was in a whole new kinda Kansas. I installed Term of course and after logging in discovered that yes, it has plenty of Unix in it. But alas, the screen is very small and the keyboard hard to use.
Well today in trying to solve the problem you posted here (ie, after all these mods, if it bricks and I need to reinstall everything, sheesh, how am I gonna remember what I had?), I also "discovered" that there is an FTPd program available in community sources (I jailbroke with iLiberty+, which ups the comm'y sources packages for downloadability of lotsa new and nifty programs). So, I installed the FTPd package. I already had SSH on it from the iLiberty+ upload of packages. I then downloaded the PUTty programs from out there in cyberspace onto my PC here at work, where I am Wi-Fi'ed and have an identifiable IP address assigned when I enter the network range. (IP address is displayed in BossPrefs, also installed from comm'y sources after jailbreaking, next to the WiFi config toggle).
I fired up PSFTP.exe and ftp'd into my iPod touch using the reported IP address. And it worked. I cd'd to root dir and used "mget -r *" to copy back every dat-burned file on my iPod. In fact, it's still copying now as I write!
I also used putty.exe to open an SSH window to the unit, and yes, it worked-- took a little while for the conn to get est'd but after about a minute, it took. So there I was, a full screen in front of me, a real keyboard, and an open root session to my iPod!
Is this not the very definition of happiness for the budding gadget geek?
BTW, for folks new to Unix, before you mess with your iPod at this level, puhhleeze, get some practice first on a machine of some kind you can afford to mess up. Also for those new to FreeBSD, the default root pwd for the system is "alpine". You should change the "root" userid pwd right after logging in by using the 'passwd' command to something else, as you don't want some hacker to get into your unit while you are messing about in a place with public Wi-Fi, to which you may be connected w/out knowing it.
If this iPod ever bricks, I will try to restore it with the backed up files after reviving it and installing the FTPd program after jailbreaking the unit again.
However I do not know if that will work. I am merely telling you this stuff because it *may* be a way to back up *all* your iPod stuff in case of bricking. I don't know for sure based on experience that a unit would be successfully restored using the backed-up files transferred over to another PC merely by mput-ting them back onto the unit over FTP. Time will tell, I guess, but I hope no time soon!