Lomo Pro is a very simple photo editing tool. It lets you open your photos and apply what the developer calls "lomo styles". I had honestly never heard of that. They are basically filters and there are 38 different ones for you to choose. You can load your photos by clicking on the "Add" button, which will bring up a Finder window where you can locate your files. Unfortunately, drag and drop isn't available. Also, you can only apply effects to one image at the time.
The graphical user interface consists of two panes. The one on the left has all the available filters, grouped in four different pages that you can navigate by clicking on the buttons at the bottom. The right pane shows your photo, and this is where the effects are previewed. You can simply click on one of the filters to apply them to the picture. Above the image is a toolbar that lets you open and save files, rotate the image, and access the help.
The supported output formats are JPEG, PNG, BMP, GIF and TIFF. You can use a slider to change the quality of the image but the application doesn't show you an estimated size for your files.
In short, Lomo Pro, can be useful if you want to apply some filters to a few of your photos. If you want to edit more than 5 or so pictures, then you should look for an application that supports batch processing.