I just use this:
http://www.comparestoreprices....itality-dual-clean.jpg
$20 at CVS, rechargeable battery mount (I just keep it plugged in all day, but it purportedly has a 16 day battery life), with some Colgate total paste and floss every night. My dentist had nothing to complain about at my last cleaning/x-rays (a week ago).
Unless your teeth are in dire shape, or are otherwise weak due to genetics (thin enamel and whatnot) I fail to see the need.
Edit: If you want healthy gums, you need to floss constantly. Listerine won't do the job nearly as well, despite what their advertisements may say.
