Update: Some users are reporting that the update is disabling cell service and TouchID buttons on some phones. I can confirm that this happened on my AT&T iPhone 6, though a Verizon iPhone 5 still seems to be getting service just fine. For now we recommend holding off—do not download and install this update yet.
Update 2: Apple has pulled the 8.0.1 update. Affected iPhone 6 users are allegedly being told by Apple support to try restoring their phones with iTunes.
Update 3: On our iPhone 6, restoring through iTunes has re-installed iOS 8.0 and it appears to be working normally. This process erases your data from the phone, but it appears to be the best way to get back up and running as of this writing.
Original story: Apple has just released iOS 8.0.1, the first update to the new operating system that reached the public last week. The update is available through iTunes or as an over-the-air update for any device that runs iOS 8—the iPhone 4S or newer, iPad 2 or newer, and the fifth-generation iPod Touch.
Though it comes just a week after iOS 8's release, the 8.0.1 update fixes a wide-ranging list of problems. Apple has fixed the bug that was keeping HealthKit-compatible apps from working, and it corrected a problem where third-party keyboards could be toggled off after entering a passcode. The company also addressed photo library access for third-party apps, "unexpected cellular data usage when receiving SMS/MMS messages," the Ask To Buy feature of Family Sharing, something keeping ringtones from being restored from iCloud backups, and "a bug that prevented uploading photos and videos from Safari."
Those updates are available for all devices, but the new iPhone 6 and 6 Plus get one specific fix that is meant to make the Reachability feature more consistent.
These small bugfix updates will continue to roll out in the coming weeks and months, so if you're having a specific problem that isn't addressed here, Apple will hopefully get to it soon (it released six point updates between the release of iOS 7.0 and 7.1). We would also expect a small update to be released alongside OS X Yosemite to enable the SMS handoff feature and other fixes for Continuity. And if Apple refreshes the iPad lineup as it has for the past two Octobers, those devices commonly come with new iOS updates as well.