I now subscribe to the £5/month unlimited service and I'm so glad that I signed up. I listen to new music pretty much all day at work thanks to Spotify and now I don't have to turn the volume down on my headphones whenever an advert comes on. It really is a small price to pay considering the vast amount of music that you get access to.

Having said that most people I know don't pay the subscription but I believe adding a small extra incentive such as 2-3 free songs per month might well convert them to becoming subscribers.