Some companies are genuinely concerned. When I left a major corp, the VP of Software Development called me into his office and said (paraphrasing) "since you're leaving I can count on you to be honest with me. Are our diversity programs doing anything useful or are we just kidding ourselves?"
The company I went to after that (another large corporation) hired a consultant to interview a set of women and minorities to try to understand how comfortable they felt in their day-to-day roles. Again, knowing the HR people there, I felt they were genuinely trying to foster a pleasant environment, but that's also the company where I came across that one black developer.
Then again, I do recall travelling across the country to be my company's Expert for a deposition for a lawsuit over a project I was on and having the opposing party think I was the cab driver...