OK, so here is the test layout and progression:
Driver Version - Game result
PM: Planetary Management Screen
GM: Game Map Screen (varying zoom levels)
334.89 - PM: Smooth Planetary management screen background with moon. GM: usual turn cycle delays at relative zoom levels.
337.88 - PM: Choppy planet rotation until moon rotates into view, then planet rotation is smooth. GM: noticeable delays in turn cycle from 334.89, also with skipping graphics (planetary moons, frame jumps) just after a turn cycle.
335.23 - PM: Initial chop in planet rotation, clear up after a second, but before the moon rotates into view. GM: initial timing delay consistent with 334.89 performance. No graphical issues noticed after turn cycle. Much improved from 337.88 "upgrade".
As of this point, I will be staying with 335.23 until the next game update.