Decent enough. Especially if you're doing a Dark Helmet costume. If you have a good MP3 setup though, you may want to just go with that. LMK if you need one (Rubies' "breather").
It's not quite loud enough (or a clean enough sample) for me, so I use a clean MP3 cycled through my iPod going to a waist amp. But it's cheap and works in a pinch.