Start on the upside: as far as portable headphones go (for the price I paid for them of around £25) these headphones aren't bad at all. I wanted these to listen to my ipod nano on long train journeys and just for taking some time out to lye in the sun on weekends. These deliver with good all-round sound, however I still would reserve complete judgement until I've burned them in a bit more, as they're constantly getting better over time.
Bass is definately not sparse here. I find the perfect equaliser settings to have on a ipod or nano is, well, none at all actually! (otherwise bass can get overwhelming). Mids and highs are good. At first I thought they were rather understated, but after 10+hours use they (seem) to be making a bit more of a punch.
My biggest gripe with them is the noise you hear through the wire if tapped or brushed against something. Its not a significant issue for me, as I don't use them while walking, running etc., but I imagine this would get annoying is they were used during such times.
In summary, a good portable player headphone - not good for anything larger like a laptop or musical instrument. Comfortable enough. Do shop around though as I think £25 was a good and also fair deal (bought them in December 2008). Check out also the CX300 and Sony equivelants - EX series.