AKG AKG K412P - Reviews
Pros: Small & collapsible, inexpensive, decent sound
Cons: Comfort and isolation lacking, sound is "only" decent
I bought those primarily for my university year abroad. I simply couldn't imagine taking full-size studio cans like my K271 on the plane. As I liked my 271, I simply went for something from the same company.
In spite of a lot of negative comments, I have come to like them for what they do. At €30, they were pretty inexpensive, they fold to about the size of sunglasses, came with a bag and have proven to be pretty durable during the last 5 years.
If you keep in mind that their main objective is handiness and small size, it is understandable that they don't match full-size studio or hifi phones in terms of sound; they are nowhere as detailled, clean and non-fatiguing. They are also not capable of insane volumes without distortion. But on a busy regional train or in the economy class like hen on the perch shortcomings of that sort matter less. For those kind of applications they sound fair enough in my opinion.
At 32Ω they are easy to drive with portables. They play loud enough even with quieter headphone outputs, like on newer Sony Walkman MP3 players. Cable lenght is about 1 meter, which is exactly right.
As smart as the 3D-Axis folding mechanism is in terms of handiness, comfort is not its greatest asset, rather its greatest liability. Pressure on the ears is high and the little foam pads do little to moderate that.
Also, isolation could be better - no wonder for a semi-open design. My next travel headphones will be a closed-back design to keep out all those noises and to keep listening volumes low. AKG has put out closed variations of the 412, so those would be worth a try. Some of them also come with "real" leather-style earpads, which may improve comfort to some degree. Actually, those should fit the 412 as well, so it might be worth a shot for 412 owners in search for a little less pressure on the ears. 
As far as I'm concerned, I found a chinese seller on ebay who offers "upgrade cushions" for the 412 and related models. They're still at the customs office, but I hope they'll deliver the improvement they promise. I'll update this review when I have my new pads.