I have had to wait once for 3 1/2hrs for the OBGYN. They had all of us waiting instead of rescheduling when he got called into a c-section. Now he reschedules appointments and i'm ok with it because i would want him to be the Dr I got when I go into labour. (I'm curently 29wks pregnant with baby #2)
I have also had to wait 6hrs before for a different dr. this time it was at the cancer clinic. He is only there 1 day a month so you can't exactly reschedule with him. They found an abnormality on my toe so I was referred to the cancer clinic as a precaution. I was warned when they called with the appt time though. Apparently they are always behind at the cancer clinic. I brought a BOM that was all appique with me and cut it all out while waiting. it was great, I got lots done.