Right now I wouldn't pay for mp3s. Look at the "selection" at emusic. The only reason i know of that place was the $50 nomad II's and the 99 cent headphones promos they had.
But, if every album ever made can be provided in mp3, in high quality, from the record companies, then its worth a shot. 25 cents a track sounds fair enough to me, with the rights to get that mp3 for life for free.