Summary: As a veterinary technician, I wanted a very small & light calculator that would fit easily in my pocket. This calculator is both. I have just two minor gripes: 1) the buttons don't offer great tactile feedback; they feel smushy when I expect a click. 2) while in my pocket, it constantly saves random numbers to memory; this only bothers me because I fear it's unnecessarily using battery life. But it's solar powered, so I'm probably just paranoid.
Summary: A significant percentage of the time when I hit a button it doesn't register. I spend a lot of time double-checking every entry I make. The calculator itself is quite small, which may be contributing to the problem. This is a low-quality calculator. There are plenty of calculators where the buttons work fine. Don't waste your money.