openecu.org

Does the OpenPort 2.0 work as a generic ODB II or ODB III code reader for any vehicle, or does it only work for vehicles with the specific ECUs it is designed for?

I'm thinking I can justify buying one if it will read any ODB codes from my vehicles (as well as reflash my STi).

It should work with any OBDII compliant vehicle, providing the software you are using uses a J2534 device for its vehicle interface, and there is USB and J2534 support on your OS for OP2.
All the common communications protocol hardware interfaces are supported in OP2.