- Can it not accelerate smoothly? The graph on the page seems to imply that.
- Also on that graph, the relation between distance and speed on accelerated parts appears to be linear, but, if this is supposed to approximate constant acceleration, the relation between distance and speed squared would be linear (v^2=v0^2+2ad).
- Why did they need to develop that GUI, when there's existing software available? E.g. Pronterface. edit I see it's also a simulator so that makes sense.
On the other hand, I really like such proof-of-concept projects, small enough to understand but large enough that you can see the patterns. One can learn a lot from them, and I'll be sure to check out the code some day :)
On a related note, some shameless self-promotion: my APrinter[1] project is an open-source firmware for CNC devices, is highly portable running on many chips including STM32F4.