The 3D Touch option to open the app switcher view has also been restored having been previously removed from the original iOS 11 release.
You'll now be able to send all of the "zombie" and "vomit" emojis you want. If you have miss the downgrade window and Apple stops signing a particular firmware, then there's nothing you can do in order to downgrade iOS 11.1. Anyway, as for what it brings, you can expect new Unicode 10 emoji, like a pretzel, pie, insane face, t-rex, vampire, exploding head, shush face, vomiting face, love you gesture, and brain. You can see some of the new emoji here, in Apple's original announcement.
To update, go the Settings app General Software Update.
There are new animals including a giraffe, zebra, hedgehog, a dinosaur and a cricket. In the associated release notes, Apple highlights the addition of over 70 new emoji, along with fixes to photo handling, accessibility, and an assortment of other issues. Some existing emoji have also been updated with more realistic designs, such as the bee, dolphin, octopus, and snail. For instance, it has a patch for the recent KRACK Wi-Fi exploit, which basically gives hackers access to your network traffic - even on secure networks.
The update to iOS 11.1 also includes some bug fixes and unspecified improvements, so there's that to look forward to if you're not big on emoji.