iOS 6.1 became available on Monday, and no doubt you will want to upgrade. If you're in the habit of syncing with your desktop computer, you can simply connect your device and go into iTunes and click the Check for Update button. However, you may want to consider updating "over the air," which requires a WiFi connection. A great article on TidBITS recommeds this method of updating because the iTunes update is much larger. For example, the iPhone over-the-air update is 107 MB whereas the iTunes update is 989.5 MB. You can update your device over the air by going to Settings/General/Software Update. The article also recommends backing up first, and says to be aware that some of your settings may revert back to the default and will need to be set again.
While iOS 6.1 mainly extends LTE capability in other countries, it also has some useful new features. One of the main ones is the ability to use Siri to purchase movie tickets from Fandango. A post on iMore shows you the very simple steps to doing so, including screenshots. You simply ask Siri to find showtimes for a movie, tap on a particular showtime, and then tap Buy Tickets. The Fandango app will then launch, and you'll be able to complete your purchase.
The update also restores an iTunes Match feature that had been available earlier but then went missing. And it adds a new feature called Reset Advertising Identifier. This flushes the cache of info that's collected about you in order to give you relevant ads. Find it in Settings/General/About/Advertising.
The TidBITS article also notes other smaller features not mentioned by Apple.
CNET has reported that over 22% of users upgraded to iOS 6.1 in the first 36 hours.