if you want a preview of a track to know whether to waste your cash or not as you put it, why dont you do what the rest of us do, go to a record shop and listen, or listen to the mp3 previews on an online shop.
if you really dont like those glen wilson songs you've downloaded for free and stolen (or which ever other artist is it whose first name begins with g and surname begins with w and ends in n) then why still have them on your hard drive.
personally, im all for mp3's, to get your dj sets out there, or your live sets, to sell your latest releases via mp3, but please dont steal them via shareware sites