I really enjoy being in the headphones, being in the closed off environment, where I can block out noise distractions.....
(at tumbler) if I wasn't wearing headphones, I wasn't working very hard. I could leave my headphones off and process email and crap, go thru mindless tasks, but if I was really coding something, building something, debugging something, or working on something difficult or in-depth, I was always in my headphones.
If I'm listening to podcasts at work, I'm not working. If I'm listening to trance or ambient (my preference), especially long mixes (3-6 hour mixes), I'm working, and I can lose a day in code in the blink of an eye.
I've been thru a few different pairs of headphones over the past few years. (Marco also has a good post on that, too, tho I disagree with some of his choices)
Sennheiser 555 (open). Amazing sound. Will never break. Might get you killed by your office mates as they can clearly hear what you are listening to.
Sennheiser 380pro (closed). Great headphones, but the coiled cable is next to useless, as it weighs twice that of the headphones. I'd still have these if it wasn't for the cable
Monster Beats Studio (closed, noise cancelling). My current cans. Over priced at £350, but I got them at a steep discount (universal is the main seller of them), and Amazon has them for £230. Audio is brilliant, and while "heavy" they are not excessively heavy, and feel well built. And the cables stay out of the way. HIGHLY recommended if you can afford them, or can get them at a good discount. Only downside is that you have to have power (AAA batteries) to use them. But that's quite minor.
Now, to find a good way to get rid of visual distraction, and I'm set.