Obviously I can't speak for your school, but the one that I did would have been worth the 2 hour drive. The premed adviser did it - she had me send her my AMCAS application beforehand and she read through it and wrote down questions before I got there. She gave me a good mix of general, ethical, and personal (derived from my application) questions. She threw a couple at me that I had not thought of before. She gave me some tips at the end and I asked her how I could improve a couple of my answers. It really helped me see which answers I felt like I was prepared for and which ones still needed some work.
It was overall a good experience and helped me out on the real interview day for a couple of reasons. 1. I had to prepare for an interview before the real interview, so I felt better prepared. 2. I felt like I had a better idea of what the real interviews would be like. 3. It gave me a boost of confidence on interview day because I felt better prepared. Even though my real interviews were tough, I think that the mock one definitely helped me.
Good luck!