Organisers who don’t know what resolution their projector is in advance and don’t have enough video dongles have ruined my day a few times.
Forcing speakers to use the conference laptop. Always a disaster. I will in fact refuse to speak at places that make me do this.
It can have a negative impact on my talk when A/V people are being really aggressive about setting up my laptop, I usually know more than they do about how to adjust settings.
The conference organizers did not tell me upfront that I am not able to use my laptop on stage and my material needs to be passed to the A/V crew. As it turned out the AV crew expected a ppt presentation file which I could not provide since I use a html5 presentation kit. “Fixing” these kinds of issues right before hitting the stage sucks.
I was at a conference where I was both required to upload my slides to the conference site well in advance and then give it to the AV person after my talk. It cut into the time I could answer questions from the audience.
Having a volunteer in the room to help with AV, room set up, other issues is awesome. Most conferences have this, so it stands out when this doesn’t happen.
One conference had a projector with a bad bulb that made all my dark blue slides with white text look like yellow with white text, so I was called out in the speaker feedback for making slides that were “unreadable.”
At the first conference I talked at I wasn’t really welcomed. I just went to the room where I talked (which was very small, they could have told me) and set up my own laptop and didn’t know if I was doing the right thing. The talk went terrible because it made me even more nervous.
I’ve had a few conferences where inadequate A/V facilities were present - stuff where the room was small, so they chose to eliminate the microphone, or the projector was on a normal-sized wall, and essentially un-viewable from mid-way through the room and back.