What an unfortunate version number. He should have skipped straight to 3.0, or even 2.5. Anywho, Accordion 2.0 is an update of the scriptaculous based Accordion script.
It's quite a neat accordion, which works nested, or horizontally. If you don't like Accordion controls then you can just read all the people who hate the guy because of the writing tone he uses on his own site - yeah, seriously.