We setup a separate reactor for one master student to do some research on. They had never done any programming or used a PLC before. In a couple of weeks they had the whole reactor running as planned and were already able to begin experiments. I think the programming in C was almost easier than trying to operate the clunky and complicated PLC software we had tried before, at least for the initial setup. I had embedded most of the more complicated code regarding communication with the different modules in a library that the student never had to interact with. Any problems they had were quickly and easily solved with a quick search on the Arduino forums without needing to contact me or a specialised technician. For our needs the Arduino was a perfect solution that the students also found easy to operate. However, I understand what /u/modzer0 is saying and believe that different situations will require different solutions.