I bought one of these from eBay some months ago, because they seemed very popular, but I haven't got around to trying it out yet. Seems straight forward though.
One thing that I have noticed is the varied price range of this item. I paid £4.99 direct from Hong Kong, and have seen others being sold for as much as £20.00 plus. The one I purchased look like a quality product, so I guess most are from the same manufacturer, due to design pattern.