Good for decoupling applications where you can count on
the DC voltage you need to drive full inversion and low
"access resistance" (channel). Poor for applications where
you require low variation in C across a wide range of DC
bias (or large signal operation). CV swing can give you
harmonic distortion issues in RF and analog amplifiers.
This is why, generally, a MOS capacitor would use N+
contacts in as heavy a NWell as can be made, ensuring
that you are well into inversion even at zero volts (a
depletion-mode MOSFET structure, if you will).