As a closed-back design, the Signature Pro provides more isolation from environmental noise than open-back headphones. The headphones also limit sound "leakage," so you can watch movies in bed without disturbing the person next to you.
The S-Logic Plus design feature really opened up recordings with spatial effects, like Brian Eno's ambient "On Land" album, which projected a vast soundstage outside my head. The Signature Pro sounds better in that regard than the Grado RS1i open-back headphones. That's worth noting because closed-back headphones like the Signature Pro rarely sound as spacious as open-back designs. The Turtle Island String Quartet's take on Lennon and McCartney's "Because" sounds perfectly balanced and very pure.
You can't always assume high-end headphones will sound impressive on iPods, but the Signature Pro succeeds where other audiophile-friendly headphones fail: it played with a loud, dynamic punch and a spacious sound space.
I also watched several episodes of the "Lost: Season 2" DVD on my Mac Mini computer with the Signature Pros plugged into a $140 Fiio headphone amplifier. The show's theme music, jungle and beach surf sounds seemed to come from all around me, and I was also impressed with the clear sounds of dialog and gunshots that demonstrated the headphones' dynamic punch.
Yes, they're really expensive, but there's a lot to love about the Ultrasone Signature Pro headphones. They're comfortable to use over long listening sessions either at home or on the run, they're ruggedly built to withstand the rigors of daily wear and tear, and Ultrasone has one of the longest warranties offered by any headphone manufacturer. The Ultrasone Signature Pros are a worthwhile investment if you're shopping for full-size headphones that pair well with any genre of music.