The ICS keyboard and voice input
Google has really gone a long way in improving the system keyboard in Ice Cream Sandwich. Compared to past Android releases, the ICS keyboard is far better at predicting and correcting text, which means you can type quickly and/or sloppily and it'll almost always figure out what you're trying to say.
The new keyboard has a few nice bells and whistles, too, like built-in spell checking and a tremendously improved cut and paste system. I tend to be a fan of slide-based keyboards like Swype, but the stock Ice Cream Sandwich keyboard is good enough that I'm actually fine with -- and even enjoying -- using it.
On the voice-input front, the familiar microphone icon allows you to dictate text anywhere in the system, as it always has -- but now, text is transcribed continuously, so words show up as you're saying them instead of in one big chunk when you're finished speaking. You can also pause and stop speaking and the system will wait for you to continue instead of stopping the session. (To signal that you're finished, you press a "Done" button that appears on the screen.)
If the voice input mishears a word or two, error correction in Ice Cream Sandwich is quite easy: The system automatically underlines any words it thinks might be iffy, and then you just tap a word to see a list of likely alternatives and pick a replacement.
The many faces of the lock screen
You wouldn't think there'd be much to say about a phone's lock screen, but with Ice Cream Sandwich, this seemingly simple system component is jam-packed with tasty new treats.
If you don't set any security options, the default ICS lock screen uses a circular unlock gesture similar to what's seen in Honeycomb. The lock screen offers a lot more functionality now, catching up with options that some third-party utilities have previously offered.
For example, you can now access and interact with notifications, see album cover art and music playback controls, and jump directly to your camera without ever having to go to the home screen.
Another nice touch: When your phone is locked and you receive a call, the lock screen features a new text-and-reject feature that simultaneously declines the call and sends a message to the person explaining why you can't talk. You can pick from a list of generic responses or add your own custom message. (You can permanently edit/change the list of default responses by going into the settings section of the Phone app.)
As with past versions of Android, Ice Cream Sandwich gives you the ability to set a security pattern, password or PIN to protect your phone. It also introduces an intriguing new option: facial recognition for phone unlocking. Once configured, all you do is hold your phone in front of your your face. If all goes well, within a second or two, it recognizes your features and unlocks your device.
I found the facial recognition system to be fairly accurate and incredibly satisfying to use. In my tests, the system was able to recognize me roughly 90% of the time, even when I was wearing eyeglasses or a hat or making some silly face (for testing purposes only, of course). The times when it didn't work were usually when I was in an extreme lighting condition or holding the phone at an unusual angle. But getting your face rejected, while perhaps mildly demoralizing, is not a big deal; you just enter in a backup password or pattern and you're good to go.
Google does note that the facial recognition option is less secure than a pattern, password or PIN; a disclaimer on the phone goes as far as to tell you that "someone who looks similar to you" could potentially unlock your phone with the feature activated. Some users have reported being able to trick the system into unlocking by holding up a photo of the phone's owner; I tried and was not able to replicate that. I also tested the system with my brother, whom people often mistake for me, but the phone wouldn't unlock with his face.
The take-home message: Facial recognition is convenient, novel and impressive -- and in most cases, it's pretty secure. But if you really need to safeguard your data and can't take any chances, it might not be the right choice for you.