Well, I don't know if this is the expected behavior, but took me a while to figure out why my commands weren't running.
If your xml has a scene with autoload attribute set to "true", the onstart attribute of the krpano element will be ignored.
Code
<krpano onstart="trace('Onstart called);">
<scene name="scene0" autoload="true">
<preview type="grid(cube,16,16,512,0xCCCCCC,0xFFFFFF,0x999999);" />
</scene>
</krpano>
Removing the autoload attribute "fixed" the onstart behavior.
I think this can be useful for users of the Everpano plugin, which uses this attribute in its first scene.
Happy coding,
Djodi