I upgraded by Feisty Fawn Ubuntu to Gutsy Gibbon yesterday and all went well. The only user note I have is that you do need to be there when the packages are installed to answer an occasional dialog or question in the terminal.
I’m happy with the result. The current Ubuntu makes it extremely easy for a marginally computer literate person to make use of Linux on a desktop. The only reason I can’t advise it for many of my clients is specific professional software–dental, veterinary, and so forth. For most office tasks, a Linux desktop will do well, and if you consider the costs of upgrading Windows as things move forward, the savings is substantial.
Current versions of OpenOffice.org are sufficiently functional and easy to use for most business requirements.