I am currently using Ubuntu 11.10 . In a few weeks I plan to upgrade to 12.04. However, I have heard that upgrade can result in a broken system. So, I thought to make a clean install without formatting because I have heard that it reinstalls your system files and deletes your programs but your personal files and program preferences, which are in /home, are not deleted.
How about upgrading and, if something goes wrong, make a clean install without formatting? What are the differences between upgrade and clean install without formatting?