I have a 500mm mirror lens. It is hard to focus. And handhold. Depth of field is razor thin. Mount the camera on a tripod and make sure my glasses are clean makes it easier though not as easy as manually focusing a 28-200. Yes, there are some shots that only the 500mm will get.
Provia 100F and Velvia 100 (no F) are my goto films for color. Negative films just don't project well. The colors are all wrong, and then there's that ugly orange mask.