The best thing about mathematica is that it has so many features which can be used to solve any kind of problem in different fields like science etc., It also helps me analyse problems at an early stage itself without having much knowledge or experience with programming language but i have seen people who are not good programmers using this tool for their work very well too! Nothing as such actually!! There isn't anything bad really although sometimes when you try solving some equations (which may look simple) suddenly your computer freezes up because there's no enough memory available due lack of RAM? You need more ram otherwise everything will go fine. I highly recommend mathamatica if someone wants something fast then they should definitely use mathemticas MathLink feature instead of writing codes themselves since its way faster than doing things manually through coding languages especially those new comers. !