This is one of those topics that really gets my blood boiling. Most of the bad you hear about crickets evolves from misinformation and ignorance. And most of the issues come from bad husbandry. I have used crickets almost exclusively for years with very, very few issues. For some people roaches are not an option. My wife won't allow a roach into the house. Silly, yes I know. However the few times I used them I wasn't impressed. They hid most of the time and weren't as active as a cricket.
There are pros and cons to every feeder and crickets are no exception. I am not saying they're perfect by any means, but they are not as bad as they are made out to be by many on this forum. If you get crickets from a reputable source they should be healthy. Care for them properly and they will be a fine food source.
I hear a lot about how crickets will eat your mantis. I have never seen a cricket harm a mantis in any way, EVER. That particular point of the argument is vastly blown out of proportion. People say they stink. Yes, they have an odor but it is no worse than roach colonies in my experience and it isn't bad. Yes, they make noise. I personally don't mind the cricket noise. Yes, they may not be easiest to breed, but they're so cheap you really don't need to breed your own. As far as a mantids health and fecundity, I never saw an issue with crickets as the primary diet for a mantis. I feed my crickets like kings, and that is the real key.
I will argue in the favor of crickets as a feeder. If you need something non flying they're a great, great choice. Get them from a reputable breeder and care for them properly and you won't have any issues. Roaches are another great option that many use, not saying they'e bad or anything. The masses can continue to bash crickets, but I will continue to use them without issue.