It's quick and efficient and I can add in some grain as well as some "structure" to my files. I don't have a workflow. I just jump in and look at what I can get using the color filter presets and the three sliders. I love a crisp black and a higher value skin tone. Generally, it takes about a minute to get everything the way I want it. Quicker than opening up Photo Shop and doing it in there. The trade off is that PS has more controls and more fine-tune-ability.
SnapSeed is my favorite "cheap" app. It's playful.