So far, there is no evidence whatsoever to suggest that food irradiation is in any way harmful. I think people are naturally scared of anything that involves radiation, but the truth is, we are constantly being exposed to radiation of some sort or the other all the time. We trust scientists in other areas, I think we need to trust them about irradiated food.
No, food irradiation is not a safe method for preservation, because there is no way to know that it gets out all of the problems that could possibly arise. Stripping the electrons can likely prevent some degeneration and also help with food poisoning, but there is no way to know because you can't see it working.
I do think food irradiation is a safe method for preservation. People say there are a lot of harmful side effects to this method, but there is really no evidence that this is a dangerous way of preservation. I think people are just getting overly paranoid about this sort of thing.
There are many things being done to our food these days that the people in the food industry try to tell us is no problem and is even good for us. But we do not have enough of a history with this kind of thing to trust it and, if it adds to profits, it is probably not good for us.