So, I've been tinkering with thisretirement calculator. I changed the years to 30, but left everything else alone. The good news is that I have 100% chance of success! Great!
However, if I up the expense ratio to 1%, my percentages falls down to 96%, and at 2% ER, it my chances fall down some more to 91%.
Sure, it's only an arbitrary retirement calculator, but it's enough to show that your expense ratio do make a difference!