I use both Pandora and Last.FM.
And I've tried out the XBOX Music (nee Zune) subscription service.
Like'em all. Very good way of discovering new acts. Also a nice way to provide a semi-random soundtrack to day to day activities.
But I also buy CDs for albums I really want.
A friend of mine caught his son downloading pirate CD music off the net a few years back. He reprimanded him and signed up for a Rhapsody subscription. He figured that for the cost of one CD a month he could keep both his kids current, teach them good ethics, and avoid the potential embarrassment of a court appearance.
I'm afraid I don't see subscription services actually *dominating* anything any time soon. (This decade, at least.) The revenue they deliver to the content owners is out of line (too low by far) with what discrete sales + piracy generates.
There is room for subscriptions but they're never going to be comprehensive enough, easy enough, or cheap enough for massive consumer adoption. The content owners won't allow it.