Blockchain.info API is just another service where you give up ownership of coins to some shady company.
I would suggest either looking elsewhere or building in some more redundancy by using an additional 3rd party callback notification service. BlockChain.info's service is free, but we're getting what we pay for.
This is not true. You will always maintain control of your private keys as the private keys are both generated and encrypted/decrypted locally.
As it has been said multiple times above, the blockchain.info API is free, and the saying that you will get what you pay for will likely apply in this situation.