Reverse polarity protection - PMOS vs Schottkey diode
I'm assuming the type of circuit you are thinking of is this: -



For use on your battery powered circuit I see little to say against it. A couple of things though; you need to pick a FET with low \$V_{GS(threshold)}\$ so that the device is still offering a tiny volt drop at low battery voltages AND you'll need a FET with low \$R_{DS(on)}\$ so that at 30mA (or whatever your peak current is) the FET is dropping less than (say) 100mV.

Maybe the following FET is a decent example: -



With 1.8V gate drive it has 0.071\$\Omega\$ resistance. At 100mA drain current this device will "lose" 7.1mV.