Abstract: An annulus pressure responsive downhole tool includes a housing having a power piston slidably disposed therein. First and second pressure conducting passages communicate a well annulus exterior of the housing with first and second sides of the power piston. A metering cartridge is disposed in the second pressure conducting passage for delaying communication of relatively rapid changes in well annulus pressure to a second side of the power piston to thereby operate the power piston, and for communicating relatively slow changes in well annulus pressure to the second side of the power piston so that hydrostatic well annulus pressure is substantially balanced across the power piston as the apparatus is run into a well. A gas energized compressible liquid spring is contained in a first portion of the second pressure conducting passage between the second side of the power piston and the metering cartridge.