Try using a program called "My Backup". You can download the free version from the market place. It will back up everything, home, settings, sms, mms, apps, call history, contacts, calendar to your storage card.
I wouldn't backup:
home: any widgets or programs not installed yet will not work
settings: it's just as easy to set them back up again
contacts and calendar: if you sync with google
apps: you won't get notified of any updates when available from the restored copy.
What I do is just back up the data I want to restore and then on a piece of paper write down a map of sorts for what my home screens looked like and then I go in to the Market and downloads and write down the list of all the apps I have installed. Any apps you purchase will still be in your downloads in the market after any rom flash but all of your free apps will need to be searched again.
For the record, check out the poll I posted about the 2.1 upgrade
http://forum.ppcgeeks.com/showthread.php?t=121750, most are not happy with the decision. I personally am still runing Fresh Toast 2.1 and loving it. I will wait for the official rom to be rooted or cooked in to other custom roms.
Enjoy.