I got XmartCalculatorPro for free when they offered it, so I don’t know the price of XmartCalculatorPro but for I what can tell it’s simplicity makes it extremely useful, for example, it stores your operations on the top so that you can review the numbers if there is any doubt, that’s something that the native calculator doesn’t offer and that is presented in a very simple maner, you are allowed to customize the colors of it as well, although I have to say that when you apply a light color the font should change to a dark color so that you can see better, however, I don’t think that’s something to really drop the rating. You can quickly copy the result, edit the operation at any point, etc. About the more technical stuff I can’t really tell, I don’t use those options frecuently, I only use it as a pocket calculator to make calculations at the store or adding up simple things. I guess to answer if it is worth, it will depend on the price, but there is no doubt XmartCalculatorPro is way better than the original, I don’t know why Apple keeps doing this retro calculator, it is seriously easy to emprove it and yet we are stuck with it.