-Non permanent damages: The device uses "hooks" that grab onto the penis, but do not go deep enough to affect anything that affects function. It HURTS A LOT, but it doesn't cause any structural or functional damage - just slight discoloration.
-Still prevent rape: It may not prevent rape entirely, but it would at least take some careless rapists off the street - and just give the woman a feeling of safety and security when she's home alone. If you knew, as a potential rapist, that the woman may have something in her vagina that would hurt your penis A LOT and you couldn't remove it yourself, wouldn't you think twice?
-Leaves the women to safety after "Deployment": The man's penis is grabbed by this device, and the immense pain he feels overtakes the "rationality" receptors which would cause him to further hurt the woman. He has to try to quell the pain, and naturally the way one would expect to do this is by removing the device - he will soon realize this is an impossible task, but the victim will be long gone and he will be apprehended because of the device.
-Doesn't hurt the women while it's inside her: The design can be found on the website:
www.Rapestop.net. They have quite a good answer to this piece of criticism, basically saying that it's how the device functions that prevents accidental injury from happening. It has been tested.
-Isn't visible (not noticeable from close up): Absolutely not! It fits behind the labia and has no strings or anything protruding [taken from Rapestop.net FAQ]. You can't see behind the labia
-Won't malfunction: Of course, any product has the risk of malfunctioning. However, the harm done by these malfunctions shouldn't be a reason for the women not to be able to purchase them. It's all about risk vs. reward, and according to the products' creators, there is quite little risk with quite a high reward.
I hope these answers helped

I mean obviously, there will be some drawbacks at first. Eventually, however, this product might become more and more developed until [ideally, but impractically] it is finally able to stop rape entirely, while not harming innocent people.
And yes, I totally agree that people need to read the thread before posting