At the moment it's free. Developed by creators of digital software it lets you enhance your shots in many ways. Snapseed gives you control over brightness, saturation + contrast etc - but also a range of vintage effects and 'drama' control. Basically you just need to have a go..
Here's my first couple of swipes at it:
|straight from the 4s|
|after a few minutes on snapseed|
|with 4s, natural light, late afternoon|
|same shot, snapseed filter|
Yes, there's a lot of photography apps out there - but i think this might be in my new top 3..