I received access to Invision's Craft Prototyping beta yesterday afternoon and have since had an hour or so to play around with it and I'm impressed. Craft inside of Sketch is incredibly smooth and fast and the prototyping section is no different.
When you first open Prototype, you're asked to create a new prototype without any context of where that concept would live or be saved, which caused some slight bit of confusion as we didn't want Prototype to interfere with our current projects on Invision. As far as I know right now, the Prototype only lives locally within the file itself. I confirmed this to be true by having another designer send me a Sketch file that contained a tap-through prototype and it worked on my device no problem.
The interface reminds me of Flinto and how click-through interactions are produced. If you have an object of any kind, you simply select the object, press 'C' and link it to another artboard. After clicking, a modal will come up asking you what gesture to activate the transition with, what behavior you'd like it to do (ex: link to an artboard, link back, dismiss a modal, launch Camera, or Browse photos), and then choose what transition should happen between the two artboards.
The coolest feature by far in the Beta, are the ability to use the iPhone's camera to add a photo into the prototype. You link an object to the camera action and name the layer you'd like to import the photo to
_photo. After taking the photo, the image will appear inside wherever you've placed that photo square. Unfortunately, deviating away to another part of the prototype will remove this.
In addition to the Camera, Craft also has access for you to pop up the keyboard, create input fields that you can type in, browse for photos to insert, embedding a website into a shape (we tried this with google maps), send an email, a text, or even a phone call, all within the prototype. Talk about power.
My only issue so far with the prototypes, and I'm sure the problem will be solved quite quickly in the future, is the lack of sharing with others and testing your prototype within Sketch. With the Invision website, you can link the prototype out to others to view and it's not an issue, but you also relinquish all of the major features that Craft gives you. I'm sure with time, they'll have solved all these kinks.
If you have access to the beta, let me know what you think? I'm planning a longer write-up with all of the features in depth but for now, I'm still exploring the possibilities.