PETA's a mixed bag. They've managed to get some really good things done for animals.
Their campaign against KFC has caused the Canadian franchise to re-evaluate the way they slaughter chickens and look to moving to a more humane method than the current one which often has their guts being pulled out of them while they're still alive.
They've gotten McDonalds to move partially toward eggs from free-range chickens as opposed to eggs from 3 chickens stuffed in a 1 foot cube cage for their life, with their beaks sawed off so the animals don't peck each other to death while in there.
The are primarily responsible for the decline in the acceptance of fur among the populace, something which is extremely important when you consider that some furriers, especially in China, skin the animals while still alive.
They are primarily responsible for a large decline in animal testing where such testing is completely unwarranted, such as testing solvents etc. in the eyes of rabbits, even though human physiology is different enough as to make such tests worthless, and the solvents are never intended to be put anywhere near the eyes.
On the other hand, they go way the hell over the line in a lot of cases, being generally unconcerned about causing emotional pain to the human animal, and there being various rumours about their connection to the ALF.. a group that will occasionally cause physical suffering to humans in the pursuit of their cause. And their attacks on particular individuals I find to be pretty reprhensible. So even though I personally support a number of their goals, I've stopped providing any sort of support to their operations.. my donations go to the WWF or Humane societies instead.
Des Krieg: Your comments are a red herring. Sure, nature may be cruel, does that excuse us our own behavior? If humans lived solely according the rules of nature, we'd be up in trees flinging feces at each other. (These days we use forums, allowing our feces to fly much further) One of the priveleges and responsibilities of humanity is that we have these brains capable of ethical thinking so that we can rise above the brutality of nature.
In addition, while what you describe may be the ideal, the modern slaughterhouse processes around 400 head of cattle/hr. At those speeds, there simply isn't time to line up a clean shot every time. A fair number of cattle get strung up by their back legs, swung along a chain line, and get gutted while still alive. It's even worse for smaller animals, such as chickens which often get their wings/legs torn off while they're live by workers throwing them into bins and conveyors for later processing.
I'm not against killing for food, but I think we have a responsibility to ensure that our killing isn't any more painful than it needs be, and unless you're buying from local farmers that produce in small quantities, odds are you're supporting companies that cause needless suffering to animals in pursuit of the bottom line.