While the px-100s are insanely comfortable, light, and have excellent presentation and that open sound/feel, I dislike them because you can feel the bass vibrations right next to your skull because of its boosted bass and light weight, but i think a lot of people might actually prefer that, especially I think if you are into rap/hip hop style music.
Maybe I just dont like bass that much, cans that i hear others complaining about lack of bass response and so forth are perfectly fine for me.
These things are built really well. There is a steel reinforcement to the headband, and the cups swivel 90 degrees for storage/neck use. I've personally seen the px-100 as the headset that museums give out for audio tours, they must be rugged to survive public abuse.
I bought them when I was stuck in a country that doesnt really have online shopping and had to buy whatever was available at retail. Once i bought them I realized that 1. I never really want to use closed headphones ever again if I can avoid it and 2. It can be really hard to hear open cans with a noisy ambient environment. For that reason I always pack the px-100 in my bag, and prefer to use it, but I also always have a closed can or in-ears in there as backup.
As a caveat though, If i still lived a foot-commuter lifestyle right now Id probably get better IEMs, a hd-25ii or a vmoda m80.