I think this sim will be as good as, If not better than IRacing in terms of Physics. The guys behind this are the same ones who were behind Netkar pro and if you have played netkar you will realise just how good the physics are and this will give you some indication as to how good Asseto Corsa should be.
I for one can not wait until this is out as I think this will be the top racing sim out there and the one I shall be spending most of my time with, At the moment it seems to tick most of the boxes for me, The only exception is the support from the community, Netkar seemed to suffer from a lack of support online, even though those who played it always raved about it.