Pros: Tangle-free cable, packaging, good microphone, good build quality, decent mids and treble
Cons: Difficult fit, cable noise, little isolation, anemic sound
I bought these after my pair of Sennheiser CX-300 II's fell out of my pocket, as a short-term solution until I could find something I really wanted. The packaging on them is excellent, with the headphones in a sturdy box that you're unlikely to ever lose. Included with the headphones are five different pairs of tips, for different sized ears, a lengthy printed user manual, and the headphones themselves.
The headphones themselves are very sturdily built, and have a flat, completely tangle-free cable and an iPhone mic. The tangle-free aspect of them is very enjoyable, as you can put them anywhere, and you're not going to have to spend five minutes untangling some gordian knot in order to use them. Also, while the headphone is built entirely in plastic, they seem to be able to take a good beating. Also, the headphone jack is excellent - it's angled and very low profile, and so is very good for those who put their phone or player in their pocket.
As for wearing comfort, the a-jay four are very light, and the tip doesn't protrude much from your ear, which makes them good for wearing under a beanie or hat during winter, and it makes them very suited for using while lying on your side - they don't protrude from the ear. Also, wearing them for extended periods of time is likely to be comfortable. However, the flat cable has its ups and downs - while they provide hassle-free use, the weight of the cable is quite noticeable - the cable tugs on your ears and will easily come out, and doubly so in the case of the right-hand side, due to the weight of the microphone. Also, due to the weight of the cable, it's quite noise - move around, and you'll hear the cable bang against your cheeks. While this can be partially remedied by wearing the headphones behind your neck, it's not a complete solution, and it makes the built-in microphone and volume control next to useless.
That being said, the microphone is quite good - I've used my a-jays as a handsfree solution, and the microphone is pretty ergonomic - the volume buttons are placed on each side of the play/pause/answer button, and the buttons are differently shaped, so you can tell which button you're about to push without looking at it. Also, the microphone is usable in many conditions without having to hold it next to your mouth, even in outdoor and noisy scenarios.
So, what about the sound? Unfortunately, this is where they fall completely flat. First off, even with the rated impedance of 16 ohm, they are not particularily easy to drive, with a rated sensitivity of 96 dB. Next, there is the frequency response - I have pretty average ears - and have used any number of in-ears in the past, all of which have given me a seal with the medium/standard-sized silicone tips. With the a-jays, I never got the distinct impression that I had a seal. I could clearly hear the world around me still, and I was unable to get a proper seal even with tips that have given me a good seal when mounted to other headphones like the Sennheiser CX-300 II and CX-380, Sony MDR-75EX or the Nuforce NE-700X's.
At low volumes, the mids and highs are very pleasant. Not overly detailed, but not lacking either, and they are without any perceived peaks or dips, which means they can be worn without causing excessive listening fatigue.
But, as said above, the lack of a seal means that bass is extremely restrained, to the point of very nearly being absent. While this can be partially remedied by simply turning up the volume, that is not a good idea, because as soon as you turn up the volume, the once pleasant mids and highs takes on a shrill quality, like someone screaming in your ear.
And even if you do get a seal, this aspect of the headphones doesn't go away. When I forced a seal on them, by wrapping them, and then wrapping my earlobes over the ear canal (Yes, they do protrude so little that this is possible), the bass is still anemic.
That being said, what little bass there is isn't muddled or heavily distorted. It's there, but even if you're not a bass head, it's just too thin.
Also, the low sensitivity, and low isolation level means that as soon as you venture out of your office, you will have to turn up the sound in order to get acceptable listening levels, which leaves you with the shrill mids and highs. The unpleasantness of this sound has occurred on all devices I've tried it with: two laptops (Lenovo X201 and an MBP), an aging Sony Walkman MP3 player, the iPhone 4 and the first and third incarnations of the iPad.
So, in conclusion: Would I buy these again, or recommend them to a friend? The sound quality is, due to the lack of seal, low sensitivity and anemic bass not much better than the default Apple earbuds, and while the cable is the most hassle-free solution I've come across, it causes too much noise when moving around. So no, I suggest you look elsewhere.