Sean Ellis, writing in a post about a new product he has been working on:
With each new startup, I immediately started working to uncover the “must have” experience before I formed preconceptions about how and why a product would be useful. This involved a rigorous process for identifying the most passionate users and then getting their unstructured feedback about how they were getting value. With each new cohort of users that I engaged, I began to get more structured feedback to converge on a signal of the “must have” experience. Once I had a clear signal, I could work with the team to start aligning the business around the “must have” experience.
I also found that it was important to monitor this “must have” experience over time. Each new product update can change it. Shifts in the competitive landscape can also affect it. For an experience to be a “must have” it should be both valuable and unique. The emergence of a new competitor can instantly turn your “must have” experience into a “nice-to-have” experience.
Must-have versus nice-to-have product concepts have been around for a long time. Pills versus vitamins was another way we referred to it a decade ago.
The story for powerOne has been primarily the same and can be summed up in two words: easy and fast. Those two words have been the consistent customer must-haves for the last 15 years and we have always tried to keep those in mind while working on the product.
But the competition has exploded, too, over those years. When we released our first financial calculator, FCPlus Pro for PalmPilot, back in 1998, there was only one other financial calculator and only a couple of scientific ones for that platform. Now there are dozens of financial calculators and thousands of calculators in the iOS App Store.
The must have features have remained the same but there are a lot more products now, making it harder and harder to differentiate. We have tried — library of add-on calculations, storing your history, a simple language for creating custom templates with advanced capabilities — and will continue trying. The must-have features remain the same, though.
This has been a fun and exciting decade and a half. I hope I get to keep doing this for a long time and hope our customers continue to enjoy our efforts.
Elia Insider 
No, I don’t agree with your two words: I’d use just one: powerful. The strenght of Powerone Graph, and the reason it was way up the other sw was just this: you could do things with it that were not possible with the other ones (Mainly Graphs with all the analysys needed, and Matrix algebra). That’s why I used it and promoted it in the schools. Easy and fast there were and are many: not enough.
That’s why I still miss it, that’s why I don’t use it on the iPhone.
It looks like you don’t realize what you had in your hand: for me the Math sw was PowerOne and Mathematica, and the first when I was in a hurry..even at home.
Now…I have to find similar stuff, like MathStudio,… or use my decades old Palm.
You make a good point. I am primarily talking about our financial products. The graphing product was very easy to use for the power it provided. We took a big bet on the schools with that product and it really didn’t pay off, unfortunately.
As for adding more power to the iOS one… more coming soon. Not quite to the level of the PalmPilot version but we are adding a lot of capabilities with version 3.0, coming soon.
For the record, the version everyone refers to as really powerful for powerOne Graph was version 4. It takes time to make all that goodness!