Not very fast, not very smart
App will load an image in 3-5 seconds — pretty slow if you’re used to Picasa image viewer on Windows.
The app opens the image and reduces the size significantly. I opened a 3744x5616 image and ImageView displayed it at 345x529 but indicated it was displaying the image at 100%.
There are no options — no way to customize your view aside from the View->Change View option that changes the app background to either black or white.
Don’t waste your money on this poorly-crafted product.
GamerGremlin about Image View Studio: Gallery