Yes. the files are ordinary mp3's (i forget what bit-rate they use these days, but the files are 44Khz 16-bit for certain).
The selection on EMusic..
Apart from the odd instance where some albums are imcomplete due to record label invoked license issues (that's common to all legally operating and licensed music download sites), there is both a fairly good selection of stuff that's potentially findable in a good record/cd shop and not covered by the WMA download providers, some crossover (common both ways) and some albums are complete on E-Music where not elsewhere.
It was far better value back in it's unlimited days, where it followed the £xx per month subscription and unlimited downloads model.
However, it's definately worth a look if you have the 50 free tracks voucher or voucher code.