I attended conventions in Minnesota through the 1990s and up until 2006. I recorded a few things.
One year, I recorded the baptism talk & then got close to the pool and recorded the baptism. No one said anything; in fact, one lady came over to me and asked for a copy of the recording (her son was getting baptized).
Another year, I arrived late & so my wife and I had to sit up closer than we would've liked. We had our tripod with us &, when it came time for the talk we wanted to record, we set up the tripod right in front of my chair (I had to sit campfire-style) & began recording. One guy sitting a few chairs down from me gave me an odd look, as if so say "what's with all the commotion?" But once he saw I planned on recording, he smiled.
The only time anyone said anything remotely negative was in 2006 when I plugged my camera into a nearby wall outlet. Even then, no big deal, an attendant just asked what I was doing.
So, after bringing a video camera to ten conventions/assemblies (at least), I think I can safely say you will not be harrassed unless:
1) You giggling about it the whole time,
2) You look out of place (guys: wear a tie, ladies: wear a skirt)
3) You are totally blocking an aisle, or someone's view, or making an insane amount of noise, or using their power source.
With regards item #3, I don't blame them - they want everyone there to be able to watch & hear the whole program, if you're in the way, then it's totally reasonable that someone would say something. Even then, though, they won't say "Get that camera out of here!", they'll probably just say: "Excuse me brother/sister, but you're making it difficult for some of the friends to pay attention. Could I encourage you to move your equipment to the back of the auditorium?"