Aside from the active noise cancellation, the other noteworthy feature is the NC 495's built-in rechargeable battery, which you juice up via USB, which is nice. The Bose QC 15s use a single AA battery and offer a rechargeable battery option, though no USB charging.
As with almost all these types of headphones, you get a two-pronged adapter for airplane use. As noted, AKG also throws in an extra cloth-covered headphone cord, which is nice.
Alas, neither of AKG's noise-canceling models appears to feature an in-line remote with a built-in microphone for making cell phone calls. (Neither do the Bose headphones).
Let's start with the noise canceling itself. I wore these on a flight from New York to Las Vegas (and back) and was impressed with their noise-canceling capabilities. While they weren't as comfortable to wear over a long flight as the Bose headphones, they were on par (or at least very close to being on par) as far as muffling aircraft noise goes. They also did a decent job in the New York City subway system.
As I said, unlike Bose noise-canceling headphones, the K495s can operate without activating the noise-cancellation circuitry. Sometimes we find that some noise-canceling headphones sound better without the noise canceling engaged, but in the case of the K495s, they definitely sounded better with the noise canceling on (they sound a little bright and edgy without noise cancellation).
They sound very good--and offer good detail--but my caveat on them is that they're a little forward sounding and a little light on the bass. They also lack refinement for their high price tag. I wanted them to sound better than the Bose QC15s. I really did (we're always looking for good Bose alternatives). But they didn't.
The QC 15s are just a little clearer-sounding, more transparent, and offer more articulate bass.
Overall, I really liked the fit and finish of these AKG headphones and they certainly sound good and offer very good noise cancellation. As I said in the intro, however, they're not quite as comfortable as the Bose QC 15s and don't sound quite as good.
When you're looking at headphones at this price point, I really feel everything has to come together, especially from a comfort and performance standpoint, to earn an excellent rating overall. These guys are excellent in certain areas but merely good to very good in others. So while they're recommendable, they're not best in class, particularly for the price.