Perhaps running a search or asking some friends about what sort of headphones they'd recommend will net you a slew of responses with a bunch of different brands; Skullcandy, JVC, Audio-technica, Bose, Brookstone, Phillips, Sony, Grado, Coby, Audiovox! One of the more notable ones in this group, however, is Sennheiser, renowned for its headphone quality and price, compared to say, Bose.
Whilst searching for noise-cancelling headphones, there are a couple things to keep in mind. Price, quality, and design. The PXC250 seems to hit all three of these qualities.
The price of this set of headphones, which varies quite a bit from retailer to retailer, stays within the ballpark of $80 to $120, and it can be potentially very cheap during the holiday season (Amazon, for example, has a holiday sale discount and its price is now $57, pretty much a fraction of the normal manufacturer's recommended selling price). However, the one thing that sets it apart from a lot of other headphones is that it has a noise cancelling device, and it's considerably cheaper compared to a lot of other noise cancelling headphones (see: Bose).
The sound quality is pretty much crystal clear most of the time, if in a perfectly quiet environment. In fact, sometimes the noise cancelling device is hardly even needed if you're in an environment without a good amount of noise due to the closed ear design of the headphones blocking the ambient noise from reaching your ears. The amount of sound it blocks can vary, but the general idea is that you're focusing a lot more on the music than the ambient noise around you. In a place with loud engines, such as planes or trains, it can block as much as 60% of the ambient noise, just enough to enjoy your music, and in quieter places, pretty much all of the noise.
There are a few irks with the design quality of the headphones though. The top band feels just a bit flimsy, one of the Achilles' heels of having a lightframe design, and the sound cancelling circuit is incredibly bulky and can get in the way if you're moving around a lot. The circuit is 5 inches long and about an inch thick due to its need for two AAA batteries, and it can not be removed, which can be annoying at times. The circuit can also be odd at times, especially when the batteries are almost completely drained. In those cases, it can sometimes block out the audio output from whatever device the headphones are hooked up to, resulting in absolutely no sound whatsoever and forcing you to switch them off. Sometimes, if moving a lot, the batteries could become misaligned, causing a disrupting noise to come from the circuit, messing with the audio output. Flaws aside, the lightweight design has its own advantages. It's foldable, making it easy to carry around, and the closed ear cups have a rut near them, which can allow for both of them to lock when folding.
In conclusion, the headphones are certainly worth the price, however, if you have even more to shell out, then it'd be best to look at other alternatives. Its lightweight folding design and portability are a plus, its sound cancelling device is imperfect in design, but almost perfect when doing its job, and the comfort of using them and being able to hear almost every sound when listening makes it a worthy buy.