I severly dislike PETA. Allow me to list the reasons.
1: Approach is unproductive to counter-productive. They don't really have any plans, or any affirmative ideas, but they like to offend people and just generally do crazy shit. For example, releasing all the rats from a lab. They don't know how to live outside, and they're too many all at once, so most will just die. And who knows what condition some of those lab rats are in... I shudder to think what's being released. It has no postive effect, and generates only bad PR.
2: While animals like siberian tigers and orangutans are nearing extinction, these assholes are spending their time on cloned lab rats and dairy cows. Priorities, people. Start with the biggest threat of the biggest loss.
3: Unreasonably extreme policies. They basically expect humans to all become vegans, stop expansion of housing and resourcing, and relinquish the concept of animal ownership, all overnight. That's not going to happen, and I'm not sure that it should.
4: Emotionally unstable. PETA supporters seem to have a very hard time handling those who disagree with them and live a different life-style. They are fundamentalists, and like most fundamentalists, I think they are venting their personal problems into this weird cause.
Of course, it's easy to trash PETA, and it seems that most people do, so I'd be more interested in hearing someone try to defend them (supposing they can do it calmly and respectfully, of course).