With clamp, Dan is now sending them out with a little more clamp then he did before, should be sufficient to stay on your head and its always adjustable (he posted a how to video).
I think your main comfort issue would be with heat. I don't know where you live, but with summer coming, huge leather earpads are going to get sweaty on your head unless you are in a room with average temperature. Other than that, the comfort is amazing.
The main issue you're going to have with portability, as mentioned by soundeffect, is the size. These are not small cans. With the alpha pads, they are going to stand out. They make my large head look like big head mode from goldeneye on N64. So they won't be as sleak or stylish as the aviators might be, but they do have their own unique look, especially if you go 'darth dog' with the stickers.
The size will also make it more difficult to transport. They will easily fit inside a backpack, but it all depends on how worried you are about getting the pads squished. The build feels rugged enough, but I've had a hard time deciding to actually take them out of the house.