I've been using the new versions of the Ultrasone PROline 550, 650 and 750. The 550's sound nice but don't provide the kind of isolation I was hoping for. The Extreme Isolation Headphones are much better if isolation is the main need. The 650's are a better all-around headphone, IMO. If you're looking for super comfy cans the 750's are really nice – and are my main listening cans now. The 750's have a soft silvery velour fabric on the ear pads. It's like they massage your ears with comfy soft clouds. I fall asleep with them on lying down sometimes. But you only want to get 750's if they're going to be your own private cans. You can't really wipe the material off the way you can with vinyl-covered ear cups. I'd let some sweaty rocker use my AKG's but not the 750's.
If you haven't heard about Ultrasone's S-Logic™ system, you should check it out.
http://www.ultrasone.com/htdocs/08_...oline_index.php It's very different than having the sound blast straight into your ears - as most cans do.
I've been a long-time AKG headphone user. Still have a few 141's and 240's here. My head's a bit smaller so I usually use the 141's. But even though they're comfortable for shorter periods, I've found that after wearing them for while my ears rub on the inner element and get a wee bit sore. Still like them for tracking sometimes, though. But not using as much since I started using Ultrasone's.
I still feel like the Ultrasone's are a little hyped in the high-mids for my tastes. Not as much but in a similar way to 7506's. Some people dig that. Still looking for the perfect headphones, but the 750's will keep me happy until I find them.