The central bank deposit rate is negative in the euro area, Switzerland 2/6  BIS central bankers' speeches  and Sweden, with the main Swedish policy rate also negative. Negative rates have been effective in lowering the whole spectrum of short-term rates, and also at longer maturities via expectations. In this perspective, it has been a good complement to quantitative easing (QE).
The intention behind the policy has always been temporary – to boost aggregate demand, closing the output gap more quickly, helping to normalise inflation and subsequently interest rates. Only if central banks were to allow prolonged deflation could negative rates be considered a permanent instrument.