I have a very mixed response to these planetary improvements.
I never build them b/c I never leave serious firepower idle in planetary orbit. They clutter my build queue b/c they are never "obsolete" and they need upgrading to something useful when I capture them.
I *love* finding them on enemy worlds when I'm in a mop-up phase; one quick fleet battle is much less tedious than firing many times on a planet. (My machine is way below spec, so this stuff takes time even w/ graphics turned almost entirely off.)
I *hate* the fact that they force a fleet battle when there is only a single ship in orbit.
Please talk amongst yourselves.