The update, which is free for existing users (the app costs $4.49), is one of the most significant the app has seen in quite some time.
The dual lens support on the iPhone 7 Plus works via a toggle. You can choose between the wide angle lens (the regular camera), the telephoto lens (the one with that extra zoom) or you can put it in "Duo" mode and get a combination of the two. Having the option to explicitly choose what camera you want is a big deal because in the normal camera app, Apple will sometimes use the wide angle rather than the telephoto, even when you choose 2x zoom.
The other big feature addition is RAW support. The RAW format is preferred by professional photographers because it allows for more granular control over colours, colour balance and brightness. That means that when you edit the photos, you can get better results than with images that are simply processed by the built-in image sensor.
Camera+ supports RAW shooting for the iPhone 6S/6S Plus, the iPhone SE and the iPhone 7/7 Plus. Keep in mind that if you enable RAW shooting, the photos will take up more space on your phone. The app also supports editing of RAW photos inside its editor, known as "The Lab".
I've had a chance to play with the new Camera+ update and it's just terrific. If you've been looking for a way to enhance your new iPhone's camera, definitely check it out.