Fred - yup, that's the same conclusion I have finally arrived at. While there are many ways you can get your music for free, to me the unlimited streaming of anything you want was a big plus. No need to find it, download or rip it, copy it to your preferred location, update your media library etc etc... just to listen to something on a whim.
Now I do a quick search and press play - done! I can even save it or download it for easy access later.
I should mention I also use the Sonos system and Napster just plugs and plays nicely with it.
In my mental justification for this, I just switched phone providers and am saving over $20/month, so in my mind I get Napster for free and am still $10/month ahead. Makes sense, no?