Yesterday another team at my current client decided to try commitment-based iteration planning instead of a "fill the bucket with story points" approach. The business stakeholders had conducted a pre-planning session the day before, where we made sure the user stories had the right focus, scope, and content, and that everything was prioritized. The backlog was in excellent shape at the start of the iteration planning session.
The planning session itself went very smoothly. Instead of the usual 90-minutes of hair-pulling, the team set their iteration goals in about 25 minutes, counting 5 minutes of working through some problems with the video link (the team works in two geographically separate locations). At the end, I asked the technical team how they felt about planning by making commitments instead of by counting points. They said they hadn't completely gotten away from thinking about the points; they had done the story sizing themselves, so they remembered the sizings even though the column was hidden on the screen. On the whole, they felt it was a less stressful and more efficient approach, and they're going to try it again next week. On the customer side, all three business stakeholders said it had been the best planning session they had ever had with this team.