I've owned the Quiet Comfort 1, 2, and I just got a pair of the 15s. I wear them at work all day, almost every-day, they have averaged about 5 years of hard use per pair before each of these eventually broke.
The QC 2s sounded by far the best of the bunch on music, and had excellent noise cancellation (about 10db). The QC-15s are in another league altogether in terms of noise cancellation (>20db for most common noises), but their performance on music is only Okay (the noise cancellation is so extreme on these, that it gets in the way, IMO).
I've never heard the QC3s, but if you want noise cancellation, absolutely nothing on the market even touches the QC-15s! But I wouldn't be a bit surprised if the senheisers and/or Sonys sounded better on music.