During Office Hours the other day, several folks noted issues using NPS. Here's a study from the Service Alliance at Cambridge University that may help you build your case. The bottom line is that intention isn't same thing as behavior, and you need more than a single attitudinal measure to predict outcomes. Although the company studied had high NPS scores (65) with 70% classified Promoters, only 54% actually remained loyal. NPS is better than nothing, but its benefits are routinely oversold.