The way this hurts Apple is that some people already pass judgement on iOS 7 before it's even a finished product. When negative thoughts gets around it could damage the reputation of the OS.
This is one of the reasons Rene Richie from iMore wrote that letter for people who wanted to beta test. "Stay classy" etc.
First of all, the people that pass judgment are such a miniscule amount that its not worth it for apple's market share to be effected. Secondly, of that small number thats complaining, exactly what are they complaining about. "I don't like the icons", "I don't like the slide up for control centre", "uhhh i don't like the new notification centre", "i dont like the font" etc etc. these are all banal subjective things. They really don't matter. The core functionality of the iphone, the ease of use, the apps, the shinyness, that hasn't changed.
When a new user picks up an ios 7 device, he/she will automatically like it more than ios6. because thats how apple and good design works. it will always look newer and better. Its like a new car model coming out by a good car manufacturer, it suddenly makes the older thing, which was hotness just moments ago, seem dated.
so really the people complaining about these small things have a very small circle of influence. They can complain all they want on the forums, but to any third party outside us group of early testers they might complain to, their arguments must seem kind of insane. "waahhhh i dont like the flatter icons".
and even of that small group of complainers, really how many truly will jump ship? so in the end, a fraction of a fraction of a fraction becomes a very meaningless thing to apple. compare that to what they will gain in marketshare from a new shiny look. i dont think thats insignificant.