The good news is that an update is available that is said to fix the battery issue on the iPhone 4S. In addition, this is the first update available "over the air." No need to connect your iOS device to your computer. You can download it via Wi-Fi, though apparently not 3G or Edge. The not so good news is that according to PCWorld, some iPhone 4S users are still complaining about rapid battery drain. Yet according to Wired, it fixes the problem for most iPhone 4S users. In addition, the update fixes bugs related to iCloud Documents, adds multitouch gestures for the original iPad, and improves voice recognition for Siri users in Australia.
For instructions on how to update over the air, see ZDNet, which walks you through it, complete with screen shots. But it's actually very simple. Just go to Settings/General/Software Update. Click Download and Install. After being presented with a license agreement, the process asks you to connect to a power source to save your battery during the update. But you can ignore this if you have more than 50% on your battery. If you have less, it won't work unless you're plugged in.
If you have any trouble with the update, check out OS X Daily, which gives you some troubleshooting tips, such as restartng Wi-Fi and restarting your device. Also, the post notes that sometimes Apple's servers become overloaded when an update is first available, causing timeout issues. This is one reason that manufacturers typically roll out updates gradually, such that it becomes available to some users before others.
I was pleased with the update process -- just a few minutes. And it's interesting to note that the over-the-air update comes in at 44MB, compared to hundreds of megabytes doing the update the old way.