I bought one Casio Calculator in my B.tech 1st year, around six year back and I never faced any problem with this brand so far. Thought, it is comparatively expensive as compare to other brands, but it comes with that kind of quality too.
I got the battery replaced of that calculator after two years of continous use. The display is very clear and key are very soft and gives smooth feeling. The calculator is very much durable and comes with one year warranty. Also, my brother bought one casio watch three years back and in all ways, that watch is just awesome.
Casio has been maintaining a great reputation in the market for last so many years and providing a great quality and service. I have had a nice experience with Casio brand.