I was once involved in these types of things, but am not sure that I agree with them any more. Occasionally they have their place, but when we already have more photos and footage of the horrible conditions inside farms, I think it's best that we direct what little resources we have to exposing this awful truth to the public - who is still very, very ignorant. Then consumers can make the decisions not to fund cruelty and create long-lasting effects which will save many more animals from having to go through this misery - permanently

Animals stolen from factory farms will only be replaced by more miserable animals if the demand doesn't go away. That's what broke my heart about rescuing battery hens.
How much evidence do we need? What about the Australian code of practice? That's the hardest piece of 'evidence' we have, and it has animal cruelty written all over it! You don't need to break into a factory farm to show people that the government endorses mutilating baby animals without pain relief and locking them up in spaces so tiny that they can't even move: it's on the government's website!!
When people go into factory farms or puppy mills to do an open rescue, as you know, they attract a lot of attention. Papers run photos and the TV news sometimes runs video. Open Rescues, I think, keep animal rights in the minds of the public, therefore, planting that seed in people's mind which grows slowly. That seed that whispers when someone looks at pork in a supermarket "you sure you want that?"
As well as the impact the open rescues can have on the public, the practical reasons are just as important; rescuing and liberating animals. How can we say that rescuing not just one, but many animals that are subject to absolute cruelty is a waste? Are you saying freeing a chicken from a broiler shed is simply not worth it? We vegans always say, animals feel pain like us, love like us, fear like us etc. Shouldn't that mean they deserve to be rescued like us? I think if people were treated the way factory farmed animals are, the military would engage in rescue missions. If we hope that animals will be treated with respect they deserve in years to come, and have the rights they deserve in years to come... we should take the action we wish to see in years to come.
Look at the action of the abolitionists in the 19th century, particularly the Underground Railway. Groups of people rescued slaves by taking them to northern American states and Canada were they could enjoy the ultimate right, freedom. I think there are massive links in the struggle to end slavery in the US and the animal rights movement we should all take not of. Just like animals now, slaves were not looked at as people -- but somehow, people got the public to view them as people and moreover (concerning the animals rights movement) sentient beings.
I don't know how can be serious about animal rights if we don't believe that an animal deserves to be rescued.