Even if they had such a thing it would be rendered usless by the review/rating system Apple allows. 1 Star ratings for good apps are common when people find some issue not even relative to the app to complain about. For instance, almost every subscription based magazine gets a bunch of poor ratings because people believe they shouldn't have to pay for the in-app articles if they already pay for the hard copy of that magazine. I'm not advocating the additional charge just saying that the review is really not about the app at all, but about the pricing policy set by the developer. In comparison, some 5 stars ratings are inflated by family, friends, co-workers, fans, etc. of the app developers.
I wish I had a nickel for ever 1 star rating in iTunes because someone reported that an app wouldn't load. I have had two generations of iPhones and iPads and have yet to have an app not load. I suspect a lot of these complaints stem from people who really don't understand the device and its configurations.