I will be waiting for an invite, as far as the free service goes i am not certain it can offer anything that Pandora cannot (especially being that Pandora has a mobile app for free users. However, the only draw I can think of is being able to play a specific song when wanted rather than random songs.
Ok guys, I have 20 invites to give away. I'm probably going to regret this after the avalanche of PMs, but PM me your email address if you're in the USA and I'll hook the first 20 up IF you don't already have a Spotify account.
Also, FWIW, there's only one kind of "invite" on Spotify, so EU/UK users can send invites to people in the US.