First of all, you can find AH-D310 online for as little as $32, which makes them a very good deal. Possibly better than some $50-70 headphones, even. The "R" version has a microphone and IPod control, it's a bit more expensive, but worth it if you need that. So overall the headphones are a very good replacement for a mobile phone earset, for the money
AH-D310 are Denon's cheapest/lowest AH-D model, now that the AH-P372 have apparently been killed off.
Pros: Warm. Fast dynamics, sensitive/loud, bright and airy enough for closed, good for weak players/phones. Great value as mobile phone headset.
Cons: Too bassy, sometimes honky, cups too small. "Asian midrange" bug (~220 Hz range sagging).