Only if you are mixing with other users who want to send different amounts. When mixing with the sharedcoin pool the server doesn't desire any particular output size so can deliberately add input and output combinations which mimic your own. Then when you include randomised fees into the mix it makes it almost impossible to determine the inputs used from the value of one output.
One issue with the current version is that the blockchain.info wallet app only uses uncompressed keys, especially for sharedcoin change addresses, while internally the pool uses compressed keys.
I know iPhone compatibility is a problem, but maybe you could make the pool at least occasionally use uncompressed keys, or add compressed key change as an advanced experts-only option?