There may be an imaginary division between the personalities of Mac people and PC people in this world. There may be a similar division between iTunes people and eMusic people. I'm an eMusic person. iTunes of course is the dominant online music download store, and though I haven't checked numbers, I'm sure it handily beats eMusic's total downloads several times over. While iTunes has a slick interface, big marketing bucks, the big artists and the big labels, eMusic has so much more for the true music collector. While it doesn't have the major labels, or many of the mainstream big artists (though there are some exceptions like The White Stripes), it does feature a very wide variety of indie labels and emerging artists. The monthtly subscription model (I get 65 downloads for about €15 a month) also encourages sampling and exploration. While it may not have the latest top-40 MTV stars, eMusic has a surprisingly diverse back catalogue, with huge vaults of old jazz, blues, reggae, funk, rock, experimental electro to be discovered. This is why eMusic is an important part of my music discovery habits. Its so easy to start reading about a long-ignored, genius-before-his-time disco producer from the New York underground of the 70's and 80s (see Arthur Russell) and begin sampling your way through his amazing oeuvre.
A great place to start (although one not prominently featured on eMusic's website) is the Magazine which features a selection of spotlights and 'dozens' featuring editorial glimpses into various corners of the eMusic catalogue. We're talking a really broad scope of musical journeys here. Witness, "The Psychedelic Ranger: Adventures in Peyote". While the 'dozens' feature favourite albums of a particular style, genre or other theme (like the great overview of lost disco classics from West End Records), or the favourites of a get artist (like from the late great Isaac Hayes).
Best way to see whether or not you are an eMusic person is to check it out for yourself with 50 free downloads. Leave a message or email me and I'll send you an invite, so that I get a few extra for the recommendation. :)