My group and I had a great time playing it as we had several sessions with one-shots between campaigns. Breaker of Chains fit perfectly for a 4 hour session, not counting characters creation, of course, but do not worry, there are several pretty interesting pre-built characters available in it as well.
We used the pre-generated characters for our one-shot and had a great time. It was challenging for them, but in a correct balance. Everyone had fun and although one of the characters got thorn to pieces by chains, kind of Silent Hill's movie style, they were able to finish the dungeon.
It is a great adventure, with many interesting traps and triggers, filled with creativity to challenge players and characters. On the DM's perspective, it was considerably easy to prepare and the maps are quite well detailed and clear.
Recommend to everyone wanting to run an one-session adventure that is both challenging and interesting, with options out of the ordinary.