You shouldn't knock anything until you've tried it , ask Hanso about the darkside.
TuneECU is not only for 'screwing', that is not its primary use. Its a diagnostic and maintenance tool, if you want to maintain and repair your Rocket yourself its accentual.
It just also happens to allow access to your mapping if you want, or change settings that are nothing to do with mapping or gaining performance.
Don't be too hasty to condemn.