A differentiator is a feature that is so desirable that users will be willing to use the system even if it has very limited functionality in other areas. Identifying differentiators often requires innovative thinking that redefines the problem area. Differentiators can be used to dramatically reduce MRP by shifting focus away from which features the system does not have.
A classic example of a differentiator is the Nintedo Wii. When the game console came to market it was in most respects technically inferior to its competitors, but it succeeded because of its innovative controlling device.
Another example is Google Docs (formerly Writely), which was launched with very limited word processing features, but with the ability to collaborate on a document over the web. Users found the support for web-based collaboration so useful that they were willing to forgo innumerable features in more advanced word processors. An interesting aspect of this kind of differentiator is that it is very difficult to modify established word processors to incorporate it. Web based collaboration cuts to the core of the whole architecture of a word processing application. The differentiator gives Google the double advantage of providing a feature that many users find very valuable and being difficult for competitors to copy.