Yes, the site looks all kinds of different. I screwed up and used the "upgrade to whatever new version of Mambo" script in my webhost's Fantastico tool in the control panel.
Everything was broken from that point on and using the backup file to resurrect the prior installation of Mambo was so convoluted and ridiculous a process that I just converted to Joomla altogether. I've been planning to make the switch for months but was too damned chicken to do it.
The Joomla install appears to be functioning well.
I'll be switching to a different template and fixing all the broken windows over the next few day.