One of the best calculators on the App Store but...
Calc 2M has nailed it well with this app. The interface is intuitive and the graphics is simple and clean. However, on my iPad 2, there is noticeable lag. The root functionality is also limited to square root only. I cannot root it to the power of 3,4,5,6 (as in cube root, quad root and so on) and so on, hence the 3-star rating. If the lag is fixed and more advanced rooting capabilities are added, this app will deserve a 5-star rating.