The ride does weigh each train before dispatch automatically along with wind speed to determine just how fast to actually launch the train. It ranges really from around 98kph to 103 - 104kph depending on various factors. Batwing also weigh's the gondola during the countdown to determine just how much air pressure is required to launch it for the optimum ride experience. The ride can not be launched at a speed set by the operator and i'm not 100% weather or not it can be changed in maintenance mode.
There have been incidents that have happened, that the media have not got a hold of. But in saying that they would be reasonably minor incidents... I remember a boat load of asian tourists freaking the hell out on the turntable of Wild West Falls when I was in the lift room as they had a cane toad hopping about in their boat. One of them jumped out before it reversed haha... I've never hit a ride stop button that quickly in my life...
... and then there was the time I accidentally hit an emergency stop button when a giant huntsman dropped on my head in the lift of West as well. The supervisors said they had never seen anyone run that fast... I screamed, tried to swat it away and hit the e-stop accidentally... and then ran out my door and out of the mountain... I didn't work on Wild West Falls for a month or 2 after that one... needless to say, I don't like spiders...