I have noticed that Mentor is pushing 3rd party tools to revert to ODB in liue of HKP. This is not a direct replacement! We use CST Microstripes for RF simulation that can accept both HKP and ODB. In our tests we noticed that stackup information is not provided in the ODB which requires us to manually enter the information that causes extra work for the PCB Designer to document the stackup and then the RF Engineer must enter it. With the HKP, this information is included.
Another issue we have with ODB is that it is "semi-standard". Some programs look for the matrix directory while others require the *.tgz. It is large, cumbersome to unzip and parse (time-wise), etc.