This app is a bit finicky at times, but still fully functional. I use it everyday to quickly stitch together screenshots of conversations and to make long collages to use as FB banners.
The “custom” tool has a slight learning curve, but it’s not difficult to figure it out, even without directions: just experiment with moving the arrows around and you’ll figure it out in no time.
It can be a little slow starting up, but not significantly longer than any other photo editing app I use, and it’s *never* once crashed on me.