I upgraded from a pair of UM1s because they didn't deliver the bass I wanted.  I used these while practicing the bass and listening to my iPOD.  The dual drivers really deliver a high fidelity sound with hard to believe bass for the size.  Warning: if you don't want to hear loud and clear bass that stands up in your ears, don't buy these headphones! or use an EQ.

I was looking for a set of earphones for iPOD listening during my daily commutes.  I compared the UM1s with similarly priced earphones and found these to have the best bass response and overall quality.  After about 3 months of daily listening, I still craved more bass and upgraded to the UM2s.  Most of my friends wouldn't know the difference, but if you're a bass player, you would.