The B&W P5 was released a little more than a year ago, so this review is somewhat behind the times, as it were. Nonetheless, I personally purchased this headphone last week, and have spent the last few days acquainting myself with its capabilities and observing its character. Firstly, I should point out that despite my penchant for a more 'empirical' review process than may be widely popular, I was unable to apply a comparative methodology in this review, as I recently sold my Sennheiser HD600, HD25 and AKG K26P cans, as well as KRK studio monitors to free up capital for a higher-end purchase (hopefully a Tesla T1 or Audeze LCD-2). Nonetheless, in spite of aural placebo effects, I hope to say something useful about the P5 that may aid prospective buyers.
 
 
Let us begin with the price. Here in the United Kingdom, the P5 costs at least 249 pounds (GBP), which translates in current exchange rates to about 398 USD, or 375 AUD. Note that if you're in Australia, you'll be paying approximately 499 AUD retail, so you may want to look into import options. In America, you'll likely be paying less than 300 USD street. For a portable headphone marketed largely via Apple stores, that's a fairly steep price, although considering you can pay more for some Dre Beats, perhaps the precedent has been set... On unboxing the headphones, I was fairly pleased with the build quality - it's clear that the cans are well assembled, the leather is soft, the earpads comfortable, the moving parts silent and the detachable parts elegantly designed. In this aspect, the monetary outlay seems well justified - I can imagine these headphones lasting a significantly long time, if cared for sensibly.
 
One design aspect that I was not so taken with was the questionable ergonomic decision to angle the way in which the headphone rests on the ears and dome of the head. If you learn forward (and don't have a skull that strains the headphones' capacity to stretch) the whole assembly is likely to fall off, similarly if you learn backward too much - although it seems far more pronounced when leaning forward. Here lies somewhat of a paradox - B&W has marketed these headphones as portable ones that should be able to deal with the everyday requirements of commuting, in fact one of their promotional advertisements includes the 'phones being used on a train journey. As such, it doesn't make much sense that these phones require restricted movement in order to remain comfortable - for example, if I'm walking down the street with them on my ears, I have to make sure not to automatically tilt my head down (my instinctual reaction) when making my way somewhere. In a sense this might help my posture, but it is slightly irritating that there isn't a better clamping mechanism. Then again, perhaps I'm too used to the significant force the Sennheiser HD25-i-II exerted on my ears - it used to be my previous portable choice.
 
Ergonomics and build quality aside, the sound quality of the P5 is reasonable. I think 'reasonable' is an apt adjective, primarily because my impression of the P5 over the last few days is that it has a fairly even-handed quality to it - it doesn't seem to do anything incredibly well, but manages to be an adequately capable contender when faced with a variety of genres. I should note that one area where I think the P5's do indeed shine is percussion, specifically when listening to genres like Death Metal, Dubstep and Grime (and one would imagine variations of those genres). Listening to Cryptopsy's "Once Was Not" (2005) is particularly impressive. The gravity blast in Carrionshine demands quite a lot in terms of transient response from a pair of headphones, and the P5 never blurs Flo Mounier's ferociously quick snare hits - something which the Sennheiser HD25 didn't manage as well, perhaps due to the bass notes drowning out some of the snare hits. The cymbal hits on the P5 are also particularly impressive - well defined and clear - they don't get lost in the very busy sound scheme as they can with lesser cans. Guitar solos aren't as captivating as the HD600 rendition of Nile's Annihilation of the Wicked (from memory) but that could be due to lack of volume matching and selective memory - if I take my recollection of the HD600 out of the equation, the solos are still 'satisfying' but not as clearly defined as the cymbals are from the rest of the tracks, if that makes sense. The guitar solos seem to blend a little more than what they should. Double bass (drums) is certainly visceral and impactful however, something which the HD600 didn't manage to do due lack of lower-end bass response.
 
Here's an interesting FR graph of the P5: http://www.pcmag.com/slideshow_viewer/0,3253,l%253D250334%2526a%253D249659%2526po%253D3,00.asp?p=n#fbid=PJfHUnbVYq2
 
The P5 isn't as powerful in the bass department as the Senn. HD25-i-II, but it manages to be satisfyingly meaty and textured nonetheless. I tried using the SRS Enhancement EQ on my HTC Desire HD when listening to Dubstep and despite the obvious bump to bass frequencies the SRS preset provides, the P5 doesn't distort and actually made my ears rumble - hard to describe! I now regret not using the SRS EQ with my HD25s, would have been interesting to see what they were capable of. When I'm not using the HTC Desire HD as a portable source, I use the P5 via the Asus Essence ST which is on the lowest gain setting as the headphones' impedance is lower than 32 ohms. Playing FLAC files via Foobar I couldn't really detect much of a difference, although I don't have much faith in sources changing the quality of sound, nor amplification on a headphone with impedance this low. The Asus could definitely drive the P5 much louder than the HTC Desire HD can though, which is to be expected - at reasonably high volumes (0 gain, Volume bar at 75%, Foobar @ 100%) I found the P5 to be too fatiguing to listen to for long periods, perhaps because the treble seemed to become a lot more abrasive as the volume went up in relation to the bass; it seems for bassheads (I like Dubstep too much) EQ might be the only option at listenable volumes. 
 
Soundstage on the P5 is as narrow as the HD25-i-II to my ears, I haven't yet tried any crossfeed VSTs to examine the differences the make though. It's hard to formulate positions of instruments (I used Coltrane's A Love Supreme to test this) in comparison to the HD600 iirc. Of course, considering it's a closed-back design the narrow soundstage is somewhat expected - when I purchase a higher-end open headphone I might return to the review to add some comparisons.
 
All in all it might seem that I'm somewhat negative about the P5, but the truth is that despite not being an absolute knock-out in terms of sound quality, it's hard to find anything super-incredible or significantly better within the niche the P5 fills. Its build quality and elegance combined with its even-handed performance mean that for me, it was ultimately worth the money.