Regarding wheelchairs and scooters on the buses, I have no problem letting them board first. But I will admit that I do sometimes groan when we encounter either a) a bus driver who is extremely slow in doing what they need to do, and/or b) a guest, usually in a scooter rented from an outside company, doesn't know how to drive the scooter, and takes forever to complete a 47-point-turn to get it backed onto the bus lift or ramp, and then 3 minutes of forward-back-forward-back once it's on the bus....
On the other end of the spectrum, I stand there in awe when I happen to get the combination of a speedy bus driver and an expert scooter driver (almost always their own personal scooter). They can lower the lift, zoom the scooter on at full speed backwards, get it parked and secured, and the whole thing took less than 90 seconds... (the slowest part of the process is usually waiting for the lift itself to raise/lower)
-Rob