Section 16 cashless exercises

For the benefit of one of my conservative clients, I was trying to get a sense of how companies feel about their Section 16 officers doing cashless stock option exercises directly through the broker who administers the plan.  What percentage of your clients allow this?  If you don't have clients, what is your sense on the industry attitude towards the practice, now that we've lived with Sarbanes-Oxley for six years?