Which investors are most interested the tax-exempt muni's?

Answer 1

Well, someone in a high tax bracket will get the most benefit. For someone in a lower bracket, the lower interest rate that the muni's carry could outweigh the benefits of not being taxed.

Answer 2

The numbers are closer than most people realize.

On regular savings, my bank is paying 3-4% taxable.
My tax exempt munis are paying 4-5% non-taxable.
My luck with with stocks and mutual funds has been painful (I don't think I've ever averaged 10-12% taxable on any such investment), so I'm quite happy with the munis no matter what my tax bracket is.