I used to be a big Hipstamatic fan. But I don't always like being locked into black and white when I shoot a black and white image. Their color never quite did it for me either. I tried Instagram but their effects were a bit too garish for me (plus I wasn't big on the whole sharing thing). I love the Shakeitphoto app but it's slow.
So what's a guy like me to do? Enter Snapseed from NIK software. It's an (as of now) free app that you can use for post-processing images. I love it because I can shoot using the regular camera and then process out the images I want in the style that I want. There's plenty of styles and processing options plus you can vary the intensity of each option so that you can create your own look.
It's worth checking out: http://itunes.apple.com/us/app/snapseed/id439438619?mt=8