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Appleintroduced new iPhones on Wednesday and will follow a week later by releasing iOS 9, its next mobile operating system. That may bring back some bad memories for consumers who felt chagrined by the last iOS rollout.

Last fall, when Apple released iOS 8, the previous version of the operating system, iPhone owners reported some major bugs, including one that sometimes disabled cellphone service and another that made the smartphone’s fingerprint sensor stop working.

This time around, the rollout should be smoother. Apple let the public test drive and provide feedback on early versions of iOS 9 — similar to what Microsoft did with its latest version of Windows — which should reduce the odds for nasty bugs to show up on day one.

I tested preview versions of iOS 9 for two months on multiple Apple devices, and while I found a few minor bugs, there were no significant issues. To help you acclimate to iOS 9, we have included some of the new items in the operating system that stood out as the most important: better battery life, improvements to the voice assistant Siri and big changes for iPads.

Your Questions: Apple’s New Products

Brian X. Chen and J.D. Biersdorfer are taking questions today on Apple’s panoply of just-announced products. They will answer the questions tomorrow.

BATTERY POWER The persistently annoying issue with all mobile products is the battery. Even if all you do is check email regularly and send text messages, you would be lucky to have more than 20 percent battery remaining on your device by the evening.

With iOS 9, Apple is taking multiple steps toward improving battery life. For one, if you put the iPhone facedown on a table, the phone will know not to light up with notifications because its sensors know that it isn’t faceup. For another, Apple says it revised apps across the operating system to make them run more efficiently and consume less power. And Apple added what it calls a low-power mode, which can be activated to turn off battery-hogging activities like animated wallpapers and motion effects.

For all this, Apple says consumers should get an extra hour of battery life with iOS 9’s under-the-hood improvements and three hours of extra juice with low-power mode on. In my experience testing the preview system on a new iPad Air 2 and a two-year-old iPad Mini, I didn’t experience noticeable leaps in battery performance, but an Apple spokeswoman said to reserve battery testing for the full release of the system. Stay tuned for a full set of tests.

OVERHAULED NEWS APP With iOS 9, Apple has done away with Newsstand, a folder containing apps for reading news, and replaced it with the News app. The app works like Apple’s Music app by creating lists of recommendations for articles you might like to read based on your preferences.

When you first open the News app, you are invited to add some of your favorite publications or topics you like to read, like Bon Appétit magazine or general articles on politics or food. It reformats articles into a magazinelike layout, emphasizing photos over text.

SMARTER SIRI When Apple introduced Siri, a virtual assistant that understood voice commands, four years ago, tech reviewers (including me) showered the feature with praise. But soon after consumers got their hands on new iPhones with Siri, many reported that the virtual assistant was unreliable and that its ability to communicate was limited.

Apple has fixed the latter complaint by expanding Siri’s capabilities significantly in iOS 9, though it is unclear whether the virtual assistant will survive the torrent of new requests it will inevitably receive. The assistant is, in short, better at understanding you, using the context of your data. It is also more tightly integrated into the system’s search tool.

Here is an example of a new Siri trick: You can search for photos on your device based on the date and location of the photo or the album name, saying, “Show me photos taken in Barcelona last spring,” or “Show me photos taken at Danny’s birthday.”

Siri is also now directly integrated into the search bar. Swiping to the left of the home screen brings you to the search bar. The same commands you would say to Siri can also be typed into the search bar to bring up the same results. What’s more, the search system studies your patterns to make recommendations for apps you open most frequently or actions that you perform.

MULTITASKING FOR IPADS The customers who will be most affected by iOS 9 will be those who own iPads, especially the latest high-end models. Apple added iPad features to the operating system that make the tablet act more like a traditional computer.

A major modification to the behavior of the iPad is the ability to run two apps side by side; before, a single app took up the entire screen. If you’re browsing the web with the Safari app, for example, you can swipe toward the left from the right side of the screen to choose from a list of other apps; the second app takes up a portion of the right side of the screen.

Also new is the ability to run another app while watching a video. Tapping a button inside a video shrinks it and moves it to a corner. The video can then be moved to any corner of the screen.

Not every iPad will get these features. Only the iPad Air 2, the more powerful and more expensive 9.7-inch model, can support using two apps at the same time for now. Users of less powerful iPads (the second- and third-generation iPad Mini tablets and the older iPad Air) can view two apps at the same time but interact with only one at a time. As for watching video while using another app, that can be done with all the aforementioned iPads, but not anything older.

BOTTOM LINE Should you update to iOS 9?

The rule of thumb for upgrading to a new operating system is to wait a little while for early annoying bugs to be stamped out, then upgrade when the system is more refined. Also, always create a backup of the data on your device before upgrading in case things go awry.

Based on my testing, I think it’s safe for consumers with newer Apple devices, like iPhones and iPads released in the last two years, to get the iOS 9 update in the next few months. For customers with Apple devices that are at least three years old, it is still unclear whether iOS 9 will improve performance, so wait a little longer to see what the early adopters report.