Ive been using this for a while and overall this is one of the best apps in category, especially for the price. I use this app in planning and projecting trades, as well as hypothetical adjustments to current positions and spreads.
The app is easy to use, but there are a few things that could make for a "quicker-to-use" experience. (Like remembering expiration date and last used strike position in the chain instead of having to navigate back after each selection.) in addition to the graphical projected p&l view it would be nice to have an option for a table view of projected p&l.
The other features, such as OI, volume, and max pain are also nice to see - perhaps in the future the developer could let you architect trades from this view by tapping on strikes and filling in the sizes, etc.
Again, as-is the app is one of the best for the price and is a nice tool for the option trader who spends a lot of time with an iOS device in hand and away from their platform.