Where I am if I get the bus in the morning to nursery/work with DD in the pushchair, my time normally co-incides with a lovely girl in a wheelchair using the same bus.
I know she has priority, I always let her on first (although she has offered to let me on first before and I've always said no). There has always been enough space for her wheelchair on one side of the bus and my pushchair (a small stroller) on the other side.
If the day comes when only one of us can get on, of course she is priority and I've no problem with that whatsoever. Although the buses are once every 30 mins (thank you Stagecoach) so if and when this happens I'll be late for work - but this is the fault of the crappy bus company who cram us onto tiny buses that are full and don't run often enough.
Neither of us has a problem - but judging by the looks and comments we both get from other people on the bus when they have to move themselves, or their ridiculously large suitcases, neither of us has a right to be there.
Sharing a bus with a wheelchair user isn't stressful, it's the entitled non-wheelchair users, non-pushchair pushers that tut, roll their eyes and make comments that make the journey stressful.