Dan Seifert, The Verge: The future is now. There aren’t any major visual changes in iOS 9, especially on the iPhone, and it feels very similar to iOS 8 and even iOS 7. That doesn’t mean Apple hasn’t been hard at work — iOS 9 is a much more stable experience than iOS 8 was when it launched, and there are a few new features here that are genuinely useful. But if you pay close attention, you can get a glimpse at the future Apple is planning for computers. And that future looks pretty great.

Rene Ritchie, iMore: The definitive iOS 9 review. iOS 9 takes a moment to solidify and round-out everything that’s come before, and start us towards everything that’s coming next. This includes making Siri and Search broader and more proactive, expanding Apple Pay, rebuilding Notes, adding transit to Maps, launching a News app, enhancing the QuickType keyboard and bringing multi-app multitasking to the iPad, amping up performance, extending battery life, tightening up security and privacy, and making the update process much more efficient.Absent the radical and the revolutionary, then, iOS 9 has to deliver on the promise not of more but of better. After the giant leaps, it has to stick the landing. So, does it?

Michael deAgonia, Computerworld. Polish and Stability. iOS 9 delivers on the attributes Apple is already well known for: innovation, solid design, stability and performance. Given all of the welcome additions, what is most remarkable is how fluid and responsive the OS remains. The fact that it works on devices that are now several years old is a boon, and for those with newer hardware, it’s a clear winner.

Charles Arthur, Overspill: What more could an iOS—or Android user—want? I’ve run my test phone on Low Power from 100% and got huge lifespans – around two and a half days, which included a fair bit of use. This is a big improvement. Note though that it will seriously slow down a lot of apps, and kills background refresh. But if you’re not using the phone for anything for a while, it’s great for extending the life. You’ll know it’s on: the battery icon turns an anaemic yellow. The screen brightness goes down, but I didn’t notice this particularly.

Nick Heer, Pixel Envy. The Pixel Envy review. If there’s anything I learned while using it, it’s that iOS 9 is a big release, far more than just a patch-and-refine deal. It’s clear that Apple learned a lot from building iOS 7 and 8, and the results are solid. It’s not perfect, but it remains the best mobile operating system for me. I wouldn’t have any reservations about recommending that you upgrade as soon as you can.

Brandon Chester, AnandTech: Final Words. It’s probably not surprising to hear that iOS 9 is better than iOS 8. On the iPhone I think iOS 9 brings along many smaller improvements throughout the OS, along with new APIs that developers can implement to improve the user experience. There are definitely some big changes such as the addition of Apple News and Transit in Apple Maps, but these are again just strengthening the core services of iOS rather than adding incredible new abilities and features. iOS 9 is definitely a huge release for the iPad though, and because I’ve been limited to Apple’s own applications I’ve only been able to scratch the surface of what capabilities the new multitasking features can enable. I think the iPad definitely deserved a major release that focused on it though, and it’s clear that Apple has had many of these changes in the pipeline for quite some time now.

Andrew Cunningham, Ars Technica: Thoroughly Reviewed. The worst thing we can say about the new release is that its biggest, best new contributions—the things that make the iPad feel more like its own device and less like a big iPhone—are only available to a sliver of existing devices. Slide Over and Picture-in-Picture need an iPad from 2013 or later, and the truly transformative Split View mode needs a cutting-edge model. The rest of the operating system is about spit-and-polish, taking existing features (Siri, Spotlight, Maps) and extending them in logical ways… If you’re running iOS 8, update. There’s no reason not to, and there’s nothing keeping you from doing it.

Frederico Viticci, MacStories: Five years on. In some ways, iOS 9 feels like the third and final installment of the iOS 7 saga. With San Francisco, a revised keyboard, and an interface that’s been polished across the OS, Apple’s new design language has moved past its awkward (and problematic) teenage years to accept its own style and voice. Interfaces aren’t diamonds: they’re not forever, and iOS will change again. For now, iOS 9 is, visually speaking, a culmination of the work started two years ago, ready for what comes next.

Release is scheduled for 1 p.m. Eastern, 10 a.m. Pacific, but you might to want wait a few hours before updating.

Follow Philip Elmer-DeWitt on Twitter at @philiped. Read his Apple (AAPL) coverage at fortune.com/ped or subscribe via his RSS feed.