There is nothing wrong with ECUTek or any of the open source flashing methods.
All the issues you will find lie with the tuner and the method in which they flash to the car. This is why one forum will bat off on open source, another on ECUTek another on standalone and so on. It will depend on what the tuner is most familiar with and how their style of tuning works with the limitations of the
ecu.
The software (ECUTek or open source) just allows the tuner to connect to a factory
ecu, much like the motec software allows you to connect to a motec
ecu, autronic software to autronic
ecu etc etc etc.