Delta 4 Framework for evaluating product: If your product outscores the existing solution by more than 4 in efficiency score on a scale of 1 to 10, your new user irreversibly will adopt your service, brag to their friends, and have a higher tolerance for your mistakes.
Podcast: Kunal Shah: Core Human Motivations [The Knowledge Project Ep. #141]
On a scale of 1 to 10, how efficient is the old method of booking a cab? How about booking a taxi through Uber? Subtract these two scores, and you get a simple framework to evaluate a product or service. According to Kunal, three things happen whenever the Delta of efficiency score between a new product and its existing counterpart is larger than 4.
First, it leads to irreversible behavior. Once you experience the Delta 4 better product, you will not return to the old one.
Second, your new adopters will have a higher tolerance for your mistakes. Even though some of the experience in the new product might be broken, you won't go back to the old ways. For example, you might hate Uber, but you won't be like, "I hate Uber so much that I'm going to delete this App and go back to the old inefficient way."
Third, when users discover something Delta 4, they will brag about it everywhere. This is what Kunal called a UBP (Unique Brag-worthy Proposition). Word-of-mouth can become so prominent that it becomes more important than the product's USP (Unique Selling Proposition).
You can find more details of Delta 4 Theory here.