I am a long-time user of the mac and iPhone product lines. I'm also one of your most successful salesman, although I don't actually work for Apple. For the record, I am an IT professional (working in security), a hobbyest developer, and all-around computer enthusiast. That is all true and hopefully enough to get your attention.
I've been doing a lot of research on iOS 7 and I have a few things I need you to hear. Although some of the features do have many improvements to the underlying code or functionality, you have major problems with the look and layout for just about every redesigned app.
First off, what is going on with the new icons? They look like they belong in Windows 8. Take it from me, many people who use Apple products do so because they love them, but many also use them because they hate the alternatives. Making your OS or apps look less like Apple and more like anything else only makes anything else that much more appealing. This "new" Web 2.0 look (from 10-15 years ago) is downright nasty in most cases. The glossy 3D-looking high-res icons from iOS 6 look better than icons on any other mobile platform. Why boast you have a retina display if you're going to make all the icons blocky and look like they were designed in low-detail 2D for people with eyesight issues? What's the word on Windows 8 again? What's the adoption rate looking like? Take note here, it's important.
Next up is the new look of most of the apps. Just about EVERY picture I've seen of iOS 7 shows it running on a white iPhone. The few people I know with white iPhones regretted choosing them because of how easily they show dirt, etc; but I digress. The apps are changing to black-text-on-white-background in many cases, as if it looks better that way because it suits the white device. The truth is, it looks Terrible, and probably worse on your elite-looking black devices. I love how OS X and pre-iOS 7 use grey or black backgrounds for everything! It's far easier on the eyes in the dark, looks much more badass, and possibly saves a little battery power not having to brighten so many pixels (? I'm not sure about power usage based on what's displayed - maybe the screen being on means the same power gets used regardless?) Either way, the white background for apps looks like something a grandma might want. By all means a grandma should be able to use your devices, and she should be able to choose that look if she wants, but don't force it on all of us.
Change in Life is a Good Thing. Change in code for security or stability is a good thing. Change in layout (for ease of use) *can* be a good thing if done right, but change in look-and-feel just for the sake of change is a BAD THING. People draw comfort from familiarity and don't always get used to new technology very easily. Even those who do mostly keep things the same once they've got it the way they like it.
If you insist on making these awful aesthetic changes in iOS 7, or if you simply disagree because this is just "a matter of opinion," then you really should be providing theme options so users can have the new & improved code, but with the previous (and much nicer) icons and darker themes within the apps. Give us freedom of choice if it's simply a matter of opinion! Speaking of freedom, WHY can't I delete the Stocks or Newstand apps, among others?!? Especially if I know I'll NEVER USE THEM! And why can't I make another browser the default on my iOS device? M$ got sued for IE simply being installed by default; you have Safari installed and the ONLY default allowed. Evil. WTF APPLE - YOU ARE NOT MICROSOFT. Seriously, are you looking to get sued for the same crappy business practices?
P.S. On a somewhat unrelated note, who thought up what's going on with iTunes?! I don't mean the new pain-in-the-ass layout that switches me back to this new view even after I figure out how to switch it to the old/good view. I mean how it MUST be used to sync all media to iOS devices. It's "iTUNES" and yet I have to use it to manage VIDEO? iTUNES is also the store, but only for music and VIDEO (but not OS X apps?!)? Why should a simple music player be so bloated? Why should an app for TUNES be forced on everyone as a monolithic one-stop-shop (which over-complicates using it rather than the intended 'having it all right there'). Have a Sync Center application for syncing media/libraries to iOS devices, and leave QuickTime and iTunes to be just players of their respective media types. Revise the App Store application to be just the Apple Store application for buying/downloading all apps & OS X applications, music, or video. iTunes wouldn't be so bloated, and users wouldn't have such a hard time figuring out how to put PDFs on their iPad, for example. Apple is supposed to be all about how "It Just Works" so maybe get back to that. "Sync" implies an action will be replicated - so if I delete an app from my phone, why does iTunes try to put it back on?! The app sync is pathetic in it's current implementation. I'm sick of showing friends, family, and coworkers how to use iTunes. I'm tired of explaining why iOS devices don't just show up like USB flash drives they could simply drag files to.
You're all over the place and it's getting a little embarrassing. Loosen your grip on your users' freedom to choose. I know you can do better, because for the most part your products can't be beat; but let's just say it's not Google's fault Android is eating your market share.