Actually, RotaryCraft is not perfect, too, but it is good and I like it.
Here's some things (other than electric engine issues I listed before)
1) Power system is kinda fine, but if you think about it, it looks like engines don't know about the load. Gas engine runs at a certain speed. You load it - it still runs at that speed. Try to do that with your car with manual gearbox. And thus torque works kinda unrealistically - any engine produces the same amount of torque no matter what the load is, but in real life, if you disconnect engine from it's load it will start speeding up - you can also try that while driving a car with a manual gearbox - if you disengage the clutch while maintaining the same throttle, engine will speed up pretty fast. There are some physics (well, the "rotational version" of the Newton's second law actually) explaining this and I'm pretty sure that Reika is aware about all that stuff, but I guess that might be insanely hard to code and use.
2) The bad thing it brings to us is the splitting power via shaft junction. IRL, if you have an engine powering, say, two fans if you disconnect one, the second one will just speed up, but in rotarycraft the junction will just waste power.
3) The fact that I need some sophisticated electronic stuff to load fuel and control the power of the engine. I mean... really? Gasoline or steam engines are controlled by a mechanical valve. And even gas turbines can be controlled mechanically! (well big ones can use some sort of electronic controls, but I don't think it's mandatory)
4) Gas engine is kinda fine, but I feel weird when I'm pointing it at solid wall and it doesn't mind at all. I also think that it looks kinda like a turbofan while it shouldn't, because it is designed not for thrust, but for shaft power.