Yeah it's really good, I do it like 4-5 nights a week.
You don't just get to take photos, you take them for a specific company who then claims the copyright. You upload your photos to the website so people can download them. I work for fotoparty.co.uk - we are in Manchester only (the company started about a month ago) but there are a few other companies that operate all over the UK (and all over the world).
Tillate is the biggest (tillate.com), they operate world wide and have been going for like 6 years. They don't pay you anything though.
It's also good for getting to know people, you meet TONS of people (being people you work with, promoters for clubs or just people who you have taken photos of - they often approach you in clubs and stuff).
You can also get some really good freelance jobs if your good at the job. The guy I work for was approached by Pure, a big club in Manchester and he freelances for them every Friday and Saturday - he gets hundreds of £ each night!
People will often approach you for other stuff too, like portraits and headshots if they are a model/looking to get into modelling.