Pros: Sound quality, comfort
Cons: so far, none
Had these for just over 2 months now and have a couple hundred hours with them. These are a very balanced headphone in terms of the frequency range they are capable of. Paul Barton (the man who designs PSB speakers) suggests this is 20-20,000 Hz @ ± 1.5 Hz, and I believe him.
I find these to be VERY comfortable. They weigh in at almost a pound, but a nice pleather padding on the headband and nice soft pleather ear-cups make them literally disappear. Unless I move my head in some direction with speed, I don't notice that I'm wearing them. I've had them on for over 10 hours straight, and never suffered warm or sweaty ears, or any discomfort at all. Perfect cans for my head it seems!
The removable cable is nice, and the ability to use either cup to connect the cable to is a bonus. There are 2 cables that come with these cans, but I've no use for the (included) ipod/iphone cable as I don't use an ipod/iphone. PSB also includes a pair of ear-pad replacements as well as a cleaning cloth for them and your first set of batteries.
These headphones operate in 3 different modes...Passive, Active, and Active w/Noise Cancellation. I currently have no need for the noise cancellation, so I don't use that mode. If you don't have batteries, the Passive mode offers a very nice sounding headphone experience. The Active mode offers a slightly enhanced low-end presence without disturbing the remaining frequencies and it nearly doubles the life of my Cowon D2. This enhanced low-end that PSB calls in-room feel is supposed to create a sound similar to that of your loudspeakers in your home. I can't really argue with this, as I've done and do comparisons with the M4U 2 headphones and the Stratus speakers with different music.
I've only listened to music with these cans thus far, no movies yet, but the sub-bass and bass performance is really quite good. I mostly listen to Drum & Bass (Big Bud, PFM, Logistics, LTJ Bukem, etc) and it shines through the M4U 2 as nicely (maybe even nicer than...?) as it does through my big-boy speakers (PSB Stratus). An oldie but goodie from the early 90's is a great way to hear the quality of the extension on these: LFO - LFO
I'm not the best person for describing sound-stage etc, as I listen to electronic music which really has no stage (?), but I was literally put right in the middle of the club while listening to Diana Krall - Live in Paris. There's much more "stage" in this CD than there is in any of my DnB CDs, and I can clearly hear where the music is coming from. I love what I'm hearing from these. Instruments are clearly separated and sound very real.
These are not just a "noise canceling headphone" as I've got a couple hundred hours on them without even using that feature and have enjoyed them immensely. Paul & Company (PSB) have produced a very nice set of "introductory" cans for their consumers.
edit: ssrock64, yes I compared them to the Shure SRH1440 and also to the AKG K701/K702 (I don't remember, it was a few months ago). The PSBs won that round, but IIRC both were below (if just) the PSB price.