NIK Snapseed is one of the best photography apps for your iDevices. The famous U-Point technology is easy to use and highly efficient in creating desirable custom looks. It was voted the 'Best Mobile App 2012'. I've been using Snapseed since it came on the market back in June 2011 and it has become my default mobile photo app.
Until June 7th, this app is FREE on iTunes Store. Highly recommended.