I switched to Sospenders this year. My first tournament of the year was on Murray in February. It started raining at about 5:15AM, and never stopped. I got out of the boat and into my car at about 4:00PM in the afternoon. Never had any problems with the auto-inflators going off.
As others have said, you should not (under any circumstances), wear them under clothing. You could actually hurt yourself.
Also, as mentioned, they do not qualify for PFD's in the coast guards eyes (or DNR for that matter), unless they are on you being worn.
I have not found them to be uncomfortable at all.
Tex