Additional filters, shapes, and effects can be purchased through the app. However, at time of review the app was moved to a $1.99 price and all in-app purchases were made free. Prior to review, the app was free with in-app purchases costing $1.99 each.
Adding text to a photo is also possible, in multiple colors and fonts. I'm nowhere near talented enough to truly use this and the shapes feature to add a creative flair to my photos -- but I'm sure someone out there is.