I bought these headphones about a year ago to use at college where I'm studying sound engineering.
I will start off by mentioning my few problems with them, most of which have been mentioned by other reviewers.
They are bass heavy. For most modern music, especially the dance genre's, these headphones will give you almost exactly the sound you want. However if you're planning on using these in a professional environment, working with more classical, or acoustic music you will need to keep an eye on how much bass you're rolling off.
The cord. All three metres of it. I don't think I've come across a cable that loves to get it self tangled more often in my life. Also, if you're working in a room with other people, you need to keep an eye on where all that excess is (I have had to extricate mine from the wheels of chairs in college's IT suites more than once). Finally such a long cable is hardly ideal for use while on the move. Yes, it comes with a storage reel, however this is slightly bulky, and if you're anything like me, it will have disappeared within a few weeks.
Finally, the ear pads. While these are comfy, in my experience after an hour or two of use they do begin to make the area around your ears feel warm and a bit sweaty.
Now onto the good points.
Despite their strength in the low frequencies, they also give an excellent representation of those mid and high frequencies. They are a bit limited, in so far as their frequency response tops out at about 17kHz, but most people by their mid twenties are struggling to hear that high anyway, and it is very unusual to get instruments playing that high (without taking into account harmonics).
The cord. As much as in my circumstances i dislike its length, it has proven useful even for me. If you are planning on using these at home, it gives you an awful lot of freedom for a wired pair of headphones. I have found the length just about ideal for lying in bed watching tele with these on (my tele being about 80cm beyond the foot of my bed). If there's no-one likely to be around to get themselves tangled in the wire, then again, these will probably be ideal. If you're going to be using them near wheeled chairs, I would be making a point of keeping hold of that cable-tidy device though.
The noise-cancellation. I can think of only one way to describe it: brilliant. Just putting these things on makes everything so much quieter, but when you start piping in some music you're going to want to learn sign language. Short of the noisiest environments (for example the middle of a building site), with some music gently coming in, you're not going to hear a thing from the outside world. On more than one occasion while I've been listening to music on these, I've not even realised my tutor's are actually speaking.
The power. I'm not a fan of overly loud music, but when mixing I've found its useful to listen to tracks really loud, and really quietly. On the times I've wanted to listen loudly, the HD-202's have definitely delivered. While at average levels, and on your head these things are not audible to the guy sitting next to you, when you choose to give them some oomph, they can be heard across a room. On contrast, when listening really quietly, these have also delivered flawlessly. Another advantage of the noise cancellation mentioned above; you can keep your ears safe, and still appreciate your music on the bus/train.
The durability. As I mentioned earlier, I have had these around about a year. During that year they have suffered quite an amount of abuse. They've been thrown in and out of my college bag, been on a trip to Den Helder in Holland, Fuerteventura and been repeatedly dropped on the floor once I've finished with them at night. All thats happened to them until very recently, is one of the 'phones' themselves has fallen off the headband on maybe 3 occasions. On those occasions it's just snapped back on, and been fine. Recently I've had an issue with the right headphone cutting out if the wire is twisted slightly the wrong way. Frankly, I feel that this is to be expected with the amount of torture they've endured over the last year, and is almost definitely the result of mis-treatment on my part. The build quality is really rather quite good, especially for the price!
If you're looking at a pair of headphones for music production, or just because you've realised how bad in-ear earphones generally are (not to mention the ill-effects on your hearing), these are an excellent buy. At the time of writing I think these are priced around the £28 margin. More than I paid, but still worth it in my opinion. I am going to be looking at something higher in the range in the near future, but as a first stop into headphones, or as an upgrade from headphones like skull-candy's which are not designed to provide the high quality demanded by industry, these are an excellent choice.