Interesting thread everyone, i'd like to share my twopence.....
About 8 years ago i worked as a slaughterman. I'd worked in there previously as an industrial cleaner, so i was aware of how things worked etc. For 2 years i worked on the slaughterline (only pigs), i learnt most jobs there.
I only ever worked at the clean end though (the dead end), never down in the pens, stunning and sticking. To be fair to the industry, and i can only speak about the pork side, it's a highly regulated process. There are MAFF inspectors in the pens, and Meat Hygiene inspectors on the slaughterline. They are constantly checking that processes, timings, treatment laws etc are adhered to rigourously.
Any kind of mistreatment and you're shown the door, along with your slaughter licence being removed, and possible conviction. A stressed animal at the time of slaughter makes for a very pale meat, and that means less money when the meat goes to market, so it's in everyones interest to stick to the rules, and work swiftly and humanely.
My personal opinion is this;
If i'm prepared to slaughter it, butcher it, and prepare it for the table, then i'll eat it. This applies to mamals, birds and fish (oh and vegetables!)