Pros: extremely inexpensive, clearest mids I've heard in a headphone this price
Cons: extremely bass light, cheap-feeling plastic housing
I was looking for a cheap headphone to carry with me in public, something that if lost or stolen would not be a big loss to me. I bought the HD201, and was pleasantly surprised. The highs are fairly crisp, the mids are very detailed considering the price, and the lackluster bass can mostly be resolved with an amp and a bit of equalization. They can't compete with more expensive headphones on any level, but one should not expect them to.
The earpads are not very deep, so unless you have tiny ears you'll likely find them pressing against the headphones in uncomfortable ways.
They feel cheap to the touch compared to sennheiser's higher-end headphones, but they seem solid enough to toss around without them falling to bits.
If you want a pair of headphones to lend to people you don't trust with your better headphones, or to carry with you in less-than-safe inner-city type places, I'd strongly recommend these.