the Fisheye mirrors (Bus Boy makes them).. arent designed for traffic(but they are helpful).. if you try to use them for backing you will always back the wrong direction.. they are designed and EXCELLENT for seeing pedestrians or objects possibly left around your bus in front and along the side.. they are also really nice for parking.. they are also a great resource for noting traffic in lanes beside you though not good for judging distance.. I use them functionally for noting traffic but not as precise judge of it.
for lane position they help a bit, but really you should adjust your lower part of your main mirrors for blind spot and lane position.. my upper mirrors are adjusted for further back viewing and also can just see the top of the bus too so I can use it for backing where i want to be concious of tree branches , etc..
since my busses are still busses, I have clear view of front to back inside, and I have my Student mirror adjusted to be of use as a rearview mirror out the back window..
while the hard-core truckers and bus drivers will say "use your side mirrors", "dont use the windows", etc.. However the main objective is to drive, maneuver, park, and operate the bus without running into things, so I am of the mind to use all of the tools available to me for making sure I dont hit stuff...