Muni bond funds recently seem to have some of the steadiest preservation of capital of all the bond types that I track, in spite of the Puerto Rico implosion. PR (and VI) is a critical part due to non-state-taxability, yet muni funds such as HYD and HYMB no longer seem to report their exact tax-year percentage on their web sites (just impressionistic snapshots at inconvenient time frames).
In the last 365 days, most bond etf type values have converged to unchanged (last 2 years a slight gain). Exceptions were the junk bonds cratered, bank loan etfs were weak, and corp a bit soft. Treasury TLT very volatile, but along with SPY stocks netted around zero change excluding dividends. So with munis yielding 4+% and prices steady, maybe they are good even aside from fed tax benefits and a bit of state tax benefits (there isn't a "my state" etf)?