Many muni professionals shy away from option-adjusted spread (OAS) in favor of the archaic 'yield-to-worst' approach. Correct implementation would undoubtedly attract converts. Read more in Spread(ing) Confusion.
Bonds trading near or below par are much more sensitive to interest rates than reported by standard analytics systems. What happens to muni prices when rates rise? Read Dr.
Kalotay and Investortools Partner to Deliver After-Tax Muni Bond Analytics. See press release and Bond Buyer article.