A99 questions

I'm wondering whether to get an A99 and would appreciate answers to a few questions from Sony SLT experts:

1. Is the A99 likely to be more like a conventional DSLR or a m4/3 in terms of its susceptibility to dust etc on the sensor?

2. How good is the sensor-shift IS likely to be, compared with that of an Olympus OMD E-M5?

3. Am I might in thinking that only certain the lenses achieve all of the functions available on the camera? If so, which lenses are needed to preserve full functionality, and what is sacrificed by using other glass?