I bought the Sennheiser HD-429 a couple of days back. They sound good and are primarily built for honest sound reproduction rather than favoring bass or any other range of audio frequencies.
Sound Pros:
1. Sound quality: Really good compared to what you can buy in the price range.
2. Lower hearing pressure at high volumes: This may be because the sound chambers are closed using soft vinyl-like material instead of hard plastic. This does not allow the full shock of the sound to be reflected back towards the eardrum, protecting the ears (and toning down the thump to acceptable levels). However, this comes with a drawback when it comes to background-noise isolation - see cons.
3. Great sound at lower volumes: This is good for the ears. However, due to the thin material used to close the sound chambers, unless the surroundings are absolutely quiet, this advantage is lost and you have to crank up the volume (see cons).
4. Sound of the music: The sound of these headphones cannot even be compared to that of typical pop-phones (see point 5).
5. Reasonably high fidelity: The bass sounds smooth and rich whereas the vocals are crisp and clear. Mids have the required breadth in the spectrum. Higher frequencies are sharp and clear. The headphones do equal justice to various frequency ranges and you get what the recording artist put on the track. These headphones are not manufactured to ramp up output from any particular frequency range. If you expect "brain-blowing bass", go elsewhere or be really really disappointed. The overall experience is good enough for listening without disappointments or gotchas.
Sound Cons:
1. Market slot-fillers: These headphones are hard to categorize and lie in the no-mans-land between cheap and high-end. It is very obvious that these headphones were made to fill the market slot that sits between pop-phones and high-end. Cannot complain for the price, but if you are to spend Rs. 4000 for these, you'd rather save up a couple of thousand more and buy something that makes it to audiophile category. Certainly much better than ordinary cans, these are good for casual listening, like while you're doing something. Honestly, I did not find them good enough for really focusing on only music or becoming immersed in the music.
2. Poor isolation from background noise: Thin vinyl covers on the back-side of speakers (the surfaces adorned with the silver-grey Sennhieser logo) are too thin to provide any decent isolation from ambient noise.
Construction Pros:
1. Cable: I found this cable to be very peculiar. It is thin, remarkably non-intrusive and does a rather good job of staying out of the way; it does not make its presence felt all the time like headphone cables do. It does not conduct sound to the listening chambers when tapped or rubbed by fingers (or fabric) during normal use.
2. Connector/pin: 3.5 mm gold-plated connector. Comes with a bigger adapter for home-theater and larger systems. Stays in very well and slides in and out rather smoothly compared to lower-end speaker/headphone connectors.
3. Fairly well-built: These headphones have good overall build quality and look as if they will last for a long time with proper use and care. That said, be warned that they have rotating joints in more than one place and I don't think that they will stand up to intentional abuse very well.
4. Well-fitting and comfortable: The headphone cups have both transverse and lateral movement to ensure a comfortable fit and this makes them good for wearing for hours together. The cushions are of very good quality and do not make your ears heat up even after hours of use. These headphones are unexpectedly pleasant and comfortable for headphones that fit around the ears. Band of the headphones is of good quality and well-built; that said, be warned that it does not look cut out for intentional physical abuse.
Construction Cons:
1. Solidness: These headphones don't feel as solid as the cheaper HD-205 II. That said, they do have a pretty decent build quality (see above).
2. Fabric: The fabric used to upholster the ear-pads and headband is pretty thin and looks it will tear if subjected to even mild abuse. I haven't tested this and will not do so, since I have bought them with my hard-earned money.
3. Cable gauge: The cable is thinner than what you'd expect on headphones of this size. You'd expect it to snap more easily, thinking from long-term-usage and durability perspective.
4. Cable length: The cable is so long that it is a hinderance for portable usage, like with mobile phones and portable audio players. The sheer amount of cable lying between your pocket to the headphone is so much that it requires special tying up (search YouTube for "headphone cable management"). Sennheiser really should have provided with a shorter cable (with the option of buying an extension cable for those who really need a long cable). That said, those who need a long cable will be extremely happy, considering the light weight and mild dynamics of the cable which make it feel absent. You'll have to be careful not to snap it while using its superlative length, though, given its thinness.
5. Portability: The cups don't fold up and are large. It is impossible to pack these up without the threat of breaking them.