That is an interesting comment about histograms. I find that reading the histogram and the highlight warnings are extremely useful to get to a good ballpark exposure in a hurry. Then I do the rest in RAW conversion.

I would also think a custom white balance with a white white piece of cardboard or paper would be as good as or better than the expodisc gadget.

A new camera is not going to change basic exposure 1/250 at f6.3 and ISO400 is going to yield the same exposure no matter how new the camera. Granted the newer cameras have better image quality at high ISO's but that is different.

Shooting cats from a tripod? Perhaps, but only sleeping cats. I shoot landscapes and human portraits from a tripod, never cats.