Look carefully at what you want it to do. If you want to do any production PCBs - even for very short runs, then pCB milling is a non starter. If you are doing prototypes and you can afford to wait a week or two, then again it isn't worth it. If you are doing prototyping at low speds it is better to use Veroboard or similar techinques.

Where PCB milling scores is where you need a prototype within hours, or perhaps days but the components are not available in non-SMT, or where you want to investigate high frequency layouts - such as switch mode PSUs, BLDC controllers etc..