I don´t like ShiVa.
The scripting documentation is bad and I really hate its lua interface, those stupid events and states. I mean, I really don´t want to receive an event from within my "main ai" which is triggered if a key was pressed and send that event to each object which is meant to react to it, where this object then has to set a local variable corresponding to the event so that it can finally use it within its onRenderFrame event or whatever it is called, to move the object as long as the key is pressed and then there has to be the same procedure for a key not being pressed anymore.
There are some strange triggers, which are kinda slow and the raytracing is really at a low level. Even in the examples, the physics player keeps moving for a moment after one wants him to stop. One could apply a force into the opposite direction, but the documentation isn´t clear about the different functions so that I have troubles figuring out the strength of the needed force. I am also missing something like gamestudios vec_rotate and vec_for_angle as well as vec_to_angle. Even though the second and third ones aren´t that hard to do yourself.
The scripting editor is nice though, as well as that GUI editor.
But the scripting itself is in a big contrast to the very high level editor. I personally don´t like its very closed Shader system.
At least it seems to be quite fast on the iPhone and it is cheap. But still I would never recommend that engine to anyone. A7/A8 and Unity are much better choices and C4 and Torque probably as well.