I decided to make my first really complex TikZ drawing: A diagram explaining the implementation of an Optimal Control Theory algorithm I did recently. There is a print version:

In addition to that, there are some animated presentation slides, explaining three variations of the algorithm:

The process of creating these diagrams was fairly involved, but not more than I would have expected. I don't think any other tool would have been up to the task, and the result is quite exhilarating. The principles of TeX/TikZ make it quite easy to create variations of existing pictures.