I'm pretty happy with them. I'm fairly easily distracted by noises: Heavy walking noises, talking, laughing, phones ringing, folks rustling potato chip bags... It can all mess up my concentration if it comes at an inopportune moment. I'm the only programmer here so most of the folks here do not understand how easy it can be to derail someone that's coding when you catch them in the middle of a thought.
Anyway, now I feel like I work in 'silence.' I have my music playing at a much lower volume than I used to and cannot hear the office antics.
These specific headphones fit over and around ear (they provide a fairly good seal which muffles out a decent amount of sound even when they're not turned on.) Once turned on, most noises disappear. Sometimes I can still hear voices but they sound like they're very far away. A little music at low volume tends to filter out the remainder of the "very far away" voices.
The battery life is about 36 hours of active use time. The headphones have a switch on the side to turn them off. Music cannot be played through the headphones when they are 'off.' The headset takes 1 AAA battery, so I just keep some rechargeable batteries on the shelf behind me.
These have their pros/cons like pretty much anything.
My apologies for rambling. :)
OH! I will add, if you have these things on your head and switched 'on' but do not have any sound playing.... you'll feel... odd initially. I felt slightly disoriented when I first put them on my head sans music. I guess it was a mild sensory deprivation thing.
edit
Also, if you just happen to not like Bose, check out the amazon link anyway. The top most customer review compares the headphones to similar models from two other brands and lists pro/cons of those models as well.