I've only ever used NTILE once and it was for a reporting request where they wanted a customer list and only wanted part of the customer base ranked by certain criteria. I don't recall the specific criteria now but basically they wanted customers ranked by income range (per survey data) but they only wanted to see basically the 50-75% range I think. So not the highest income level but not the lowest either. It was marketing data and they wanted to target a certain set of customers. As Tom mentioned, it is a very useful function but only for certain circumstances.