I'vebefore. It's a great way for independent musicians to sell their recordings.
For a one-time fee of $35 per album, it will set up both mail-order distribution (for which it takes $4 per CD) and digital distribution through all the major music stores, including iTunes (for which it takes 9 percent of what the store gives its artists, which is usually about 60 percent of the list price).
A couple days ago, CD Baby began offering direct downloads from its site. According to an e-mail I got from a representative, CD Baby takes only 9 percent of the list price--its standard cut for all digital downloads. But there's no other party involved, which means that the artist gets to keep 91 percent of the revenue from sales through the site.
As with physical CD sales, the artist gets to set the price. Downloads are unprotected MP3s, lacking digital rights management (DRM) technology, which means that they'll play on any computer or portable device. iTunes still offers better exposure--direct integration into the software used by more than 100 million iPods--but this puts CD Baby into the same space as eMusic, which recently surpassed 100 million downloads.
eMusic works with independent labels, so its artists are probably more prominent than those on CD Baby--musicians on indie labels might get some radio play on college radio and perhaps national press coverage, while unsigned bands almost never do.
Nonetheless, if you're interested in a broad array of music and like to support artists (particularly favorite local acts) well before anybody else has discovered them, CD Baby is a great place to start.