This program is not finished. Surely there are other formulæ out there that are hard enough to calculate that most people don't even bother. So, what do you think f/Calc should be able to calculate? Naturally, I am not interested in a major departure from the program's current "feel". For example, a "development timer" tab would not be appropriate at all.
You can email me suggestions for features you want to see in future versions. There is an online wish list showing all the features that have been proposed to date. If the feature you want is on that list, send me an email asking for it. The features I choose for the next version depend mainly on the amount of "votes" I get from users.