The list of new features isn't extensive and largely consists of bug fixes and interface tweaks. That said, there are a couple of useful additions. Here are the highlights that Apple has listed in iOS 5.1's documentation.
A Japanese Siri
This was the only feature of iOS 5.1 that Apple CEO Tim Cook specifically mentioned during his time onstage. Siri, the voice assistant exclusive to the iPhone 4S, now will be able to understand and talk back in Japanese. Though Apple says that the new feature may not be completely available at first, I was able to switch our Verizon iPhone 4S to Japanese without any hiccups. Unfortunately, my knowledge of the language doesn't extend past simple greetings like "Good morning," but CNET's Seth Rosenblatt was able to ask a few questions like, "What is your name?" He said Siri uses a formal vocabulary, but that she responded correctly and he was able to understand her. Just keep in mind that Siri is not a translation service, so if you have her set to Japanese, she will not respond to English commands or questions. And if you're counting, Siri now can converse in four languages: Japanese, English (Australian, British, and American), French, and German.
After Photo Stream debuted as part of iCloud and iOS 5, users quickly complained that once a photo was uploaded to the feature, they couldn't delete it. Fortunately, iOS 5.1 adds that option. So go ahead and take those embarrassing photos at next weekend's party. You can remove them the next day as you nurse your hangover.
iOS 5 added a nifty lock screen shortcut that allowed users to quickly shoot a photo without having to unlock the iPhone first. The only trouble was that it wasn't always visible, particularly when you really needed it. With today's update, though, the shortcut will be present at all times. What's more, instead of pressing the camera icon to access the camera, you can now slide up the lock screen. I'm not sure the new action is all that improved, but it's there just the same.
On the iPhone 4S, the camera app now will highlight all faces that it detects when you're trying to snap an image. Of course, it won't always detect a face even when it's squarely in the frame, but when it does you'll see the green box over the person's mug.
iPad Camera app
In another small but noticeable interface tweak, the camera shutter has moved from the menu bar at the bottom of the viewfinder to the right side of the frame. And as you rotate your iPad from portrait to landscape mode, the button shifts accordingly.
iPad users also are set to get louder and clearer audio when watching television shows and movies. We haven't see a huge difference so far, but we'll never kick an improvement out of bed.
iTunes Match subscribers now will get Genius Mix and Genius playlist suggestions. Nice, perhaps, for those who use iTunes Match, but not significant to anyone else.
New podcast controls
In the last iPad-only addition, you'll see new controls for changing the playback speed on podcasts and rewinding for 30-second segments. The latter is a great feature if you miss a beat while listening to a show and want a quick and easy way to catch it again.
Updated AT&T network indicator
If you have an AT&T iPhone 4S, you may notice that a small "4G" icon is now appearing next to the signal strength meter. It will show only when your phone is connecting the carrier's HSDPA network. As we've told you a few times, classifying HSPA+ as true "4G" is a bit of a stretch, but that hasn't stopped from AT&T from doing so.
Apple also said that iOS 5.1 addresses bugs that affect battery life and fixes an issue that sometimes caused audio to drop for outgoing calls. Call quality and battery life are two things that make a phone, after all, so we welcome any fixes. We'll have to say, however, if we see performance improvements over time.
iOS 5.1 is available today through an over-the-air update or by connecting your iPhone, iPad, or iPod Touch to iTunes. We'll add more new features here as we see them, and please tell us in the Comments section if you discover any other changes. For more Apple software news, check out our first impressions of iPhoto, the new iWork apps, GarageBand, and iMovie.