Some gig pics with the 50mm 1.8 on a Nikon D90, three songs - no flash... The EXIF data is left on for anyone who's interested.
Dark with a stong back light, ISO 200 - ISO 2500, but mostly ISO 400: Hidden Door @ The Roxy Art House
Dark. Just dark. And blown out on purpose - rock'n'roll :-) . Warning: May contain male nipples, ISO 1000-1600: Your Loyal Subjects @ The Roxy Art House
And a few from a well lit venue (except for one shot with a tele-zoom and one with a wide-angle lens), ISO 1000 - 2000: Over The Wall @ Limbo
Not necessarily the greatest pictures in the world - picked mostly because they were whole sets taken in small venues almost entirely with the 50mm f/1.8.
The main reason not to buy the 50mm 1.8 @ £75 is that you can get a brand new one with a guarantee for £105. But as long as front and back lenses are scratch free, and there are no obvious scrapes, I'd take it.
It's also worth reading: What should one look for when buying a used lens