If you're a fan of eating ground up tail, hoof and bollock then I'm sure they're brilliant. Personally, I think my own shit would probably taste better and have more nutritional value.
Yeah, the worst thing about them is the effect that microwaving has on bread. Not only does it make it horrible and chewy, it also gets soggy from all the steam coming off it. Rustlers are pretty horrible, and the worst thing is they're quite expensive considering there is much better and fresher alternatives out there for cheaper.