I don't like having salary negotiations with people that could work anywhere or could start their own company. I'm humbled and honored by their decision to work with us (that decision always comes before we talk salary).
I show them the cap table, the bank accounts, and everyone else's salary in our company...and then ask them where they would like to be.
We can't do it this way forever, but for now, it means that everyone in the company feels good about where they stand. In talking to my other startup friends, our salaries are very similar to their's, so it doesn't seem to make much of a difference in the outcome.