I have Bose noise canceling headphones, and my experience with them is that they do a really good job of blocking conversational noise if you use them with music.

Same experience here. The downside is situations where people end up standing behind or near me to get my attention. Have been startled many times. Still, for an open office they seem a must have.

Get some 3M work tunes headphones. Really cheap and they work much better than active noise canceling headphones.