While Apple's new iPhone crop is light on change—the iPhone 5C is identical to its predecessor internally, while the iPhone 5S is identical externally—the firm's new mobile OS, iOS 7, marches to the beat of a different drummer. For the first time since, well, iOS was still called iPhone OS, Apple has significantly updated this platform, both visually and functionally. And while there are certainly some issues, it's mostly successful. And that will be troubling to Apple's competitors.

To be clear, iOS 7 is mostly not what I was thinking of when I complained that previous versions of iOS 6 were unsophisticated from a user experience perspective. It still features the same "whack a mole" approach to apps, where you move in and out of specific apps to get things done, and has no truly integrated experiences. But iOS 7 does provide an important—though I think incomplete—visual refresh to what was a very outdated UI. And there are some important changes under the hood.

This overview will thus focus on those two issues rather than address specific improvements to individual built-in apps, which, by the way are mostly very good anyway. But I'm looking more closely at the platform here, and discussing how this new mobile OS version compares to Microsoft's offerings and, to a lesser degree, to Windows.

The visual bit is what everyone will notice first. When I upgraded my kids' hand-me-down iPads (an iPad 2 and iPad 3, respectively) to iOS 7 last week, they were both ecstatic at the change, oohing and ahhing as they walked away. The only disappointment was that iOS 7 won't install on the 4th generation iPod touch my son also uses. Which is odd, since that is almost certainly the most popular i-device model overall from the past few years.

But back to the visuals. Depending on the screen, iOS 7 is either lush and beautiful or stark and a bit too barren, an issue that also plagues Windows Phone, by which the design of iOS 7 was quite obviously influenced. Like Windows Phone, iOS 7 uses thin and elegant-looking fonts, which can be pretty, and replaces the reprehensible "skeuomorphic" UIs from previous iOS versions—the notepad with fake torn paper corners, the felt "game table" look in Game Center, and so on—with new, purely digital designs.

The results, alas, are mixed. I didn't like the skeuomorphic iOS designs from before, but they were at least warm and friendly. But looking at the plain-Jane and starkly white screens in iOS 7—the secondary Settings screens, especially, or Calendar—I wonder whether a happy middle-ground couldn't be reached. My guess is that iOS 8, or whatever, will eventually support user-configured color schemes, and that will warm things up for those who care about such things. It's just a maturity issue, something I certainly appreciate from seeing Microsoft stumble around perfecting its Metro-based designs.

And to be fair, the flatter new look of iOS 7—again, shades of Windows Phone—can work well when app developers adopt it. This week, a few new third party apps appeared sporting the new design, and many more are no doubt on the way. Consider the Amazon Kindle app, before and after.

To wrap up the visual stuff, I like it overall, but think there are areas for improvement. Apple's not stupid: It will do so in a measured way over time.

Equally important to iOS 7, I think, are most substantive improvements that have occurred to both the user experience and the platform's underpinnings. In previous iOS versions, you could reach a system-wide Spotlight search screen by swiping left from the primary home screen. I always hated that—like the Search experience in Windows Phone, it was something I triggered inadvertently all the time—but Apple has thankfully removed it from iOS 7. Now, you can access Spotlight by swiping down from any of the Home screens (not from the edge, though, that's for some other function): And instead of appearing as a unique full screen experience, Spotlight is now inline. Nice.

Speaking of swiping, Apple is waking up to the notion of edge swiping, which permeates other mobile platforms like Android and Windows. In iOS 7, you can swipe from the left edge (in new experiences and compatible apps) to go back, creating a software-based Back function that's sorely missing in hardware. You can swipe down from the top of the screen to access the Today screen, which provides events and notifications, an idea cribbed from Android (and a good one; we need this in Windows Phone).

You can also swipe up from the bottom edge of the screen to access a new Control Center overlay that provides access to system-level settings (thanks again, Android), playback controls (thanks, Windows Phone), and some unique functions like Camera (since there's no hardware button for that) and, get this, a flashlight. Neat.

Siri has been improved in iOS 7, though I'll just admit to ignoring this feature and move on. Suffice to say that those who do enjoy speaking to their phones will continue doing so, I've always found this kind of thing to be frustrating. It's just not my thing.

The iOS multitasking screen—reached by double-tapping the Home button—now looks like the one in Windows Phone, with thumbnails for each running app. But unlike Windows Phone, you can actually manually close apps here, something that was available in previous iOS versions and is most useful.

And speaking of features I'd like to see in Windows Phone, you can now configure iOS 7's App Store to automatically download app updates. Microsoft added this feature to Windows 8.1, but since there's no notification center, you have no idea when it's happened, and I find that annoying. (Android also gets this right.)

Ultimately, when looking at iOS 7 and comparing it to Windows 8.1/Windows Phone 8, I see areas in which Apple is finally adopting some of what Microsoft got right—a modern design based in known-good principles, but sprinkled with its own unique look—and areas in which iOS actually pulls ahead of anything we have on the Microsoft side. The two biggest improvements—swipe-based access to notifications and system-level functions—were copied from Android, of course, but they're valuable.

When you add these improvements to the already impressive dominance of Apple's i-ecosystem—more and better apps than any other platform, superior digital media offerings, and of course all the hardware accessories that are custom tailored for the devices that run iOS 7—you can see the problem. We still have the advantages of hardware buttons for Back and Camera in Windows Phone, yes. And the Windows Phone OS is vastly more sophisticated than iOS, though most users couldn't care less. And that's an issue.

In the past, I wondered about the inability of the superior Windows Phone OS to compete with Apple's dated offering. But with iOS 7, that offering is a lot less dated in ways that really matter: The look of the thing, now very modern, and the way it works, now much more sophisticated. Complaining about iOS was always pretty pointless: No one who used it seemed to care that it was overly simplistic. But now its gotten a lot better. And Microsoft, in particular, is going to have to step up its game.

With iOS 7, Apple has finally crafted a software platform that is as pretty as its hardware. If you're already using a compatible i-device, upgrading to iOS 7 is a no-brainer. (Indeed, it's probably unavoidable.)