Pros: Audio quality, Value, the size, battery life
Cons: Not being able to pause a song without unlocking phone, volume can be drastic, very large screen making it hard to use rubberbands to attach amp
The HTC HD2 has amazing sound quality without an amp, but with an amp you begin to run into problems. My Fiio E11 is perfect for the size of the HD2, but the rubber bands make using a part of the screen impossible. To overcome this, I would recommend using a stickyback velcro and placing the base on your HD2 and the hooks on your amp. If you don't have an amp, you are going to find it extremely annoying to pause a song or even lowering the volume. The HTC rivals in sound quality, but not the design.