I've spent quite some time racing Downhill Mountainbikes - and believe me - the gyroscopic effect IS there - and it is very noticeable (DH bikes tend to have MUCH heavier wheels).
Riding lighter wheels has a lot of effect on acceleration and braking. Handling also improves ALOT with lighter wheels.
It also contributes to stability. But you do need to ride faster than this "wuss" (pun intended) moving at snail speed.
That might be the case... I mounted a heavy U-lock on the front forks of a mountain bike, made steering very heavy. Felt pretty similar to a heavy wheel to me.
Of course this is all subjective (my observation, and the parent's downhilling observation).
Definitely easier to steer lighter wheels regardless of speed.
Riding lighter wheels has a lot of effect on acceleration and braking. Handling also improves ALOT with lighter wheels.
It also contributes to stability. But you do need to ride faster than this "wuss" (pun intended) moving at snail speed.