Napster To Go begs the question: buy music or rent it?

So Napster To Go debuted last week, enabling subscribers to not only stream and download the service's million-plus songs, but also copy them to their portable players. Personally, I hate anything that charges me a monthly fee, but the more time I spent fiddling with NTG, the more I liked it. And it got me thinking... Is this the future of music? Will we subscribe to digital libraries instead of purchasing individual songs and albums? I'm really starting to think we will. (Cue Dave: "Have you been abducted by mind-controlling aliens again?")