The best thing about this software it's very easy to use for new users or even advanced ones who have experience with other modeling tools like MATLAB/Simulink etc., It has all basic features such as block diagram editor which makes creating models easier than ever! I didn't find any downsides in using ARTHUR so far but if there were one then maybe its price would be too high compared to competitors (MATLAB included).
If anyone wants an open source toolbox where he could create his own blocks…