It is always all about those icons. It is a first impression, and you never get a second chance at that first impression. An icon is what separates your app from your colleague's or competitor's app.
because of the templates that are available, it seems worth getting a subscription to photoshop cc. get the template and simplify generating the different sizes you need.
now the hard part... come up with a good icon idea to represent that cool app you just built!
classic line "the world doesn't need another checkmark icon"
How To Design Better App Icons from Michael Flarup on Vimeo.
or if you prefer to read about it :)