For piece of mind (what I do) SSH into your phone and make copies of these files:
http://picasaweb.google.com/kapolani...27902441430930
That way if you ever mess up during a restore/upgrade you can always get your info back.
**edit**
For people who can't check the link to Picasa:
/var/mobile/Library/AddressBook - contacts
/var/mobile/Library/Calendar - your calendar
/var/mobile/Library/Notes - your notes database
/var/mobile/Library/Safari - bookmarks etc
/var/mobile/Library/SMS - your texts
There are other things you can copy i.e. sbssettings, cydia apps, blah blah blah.