So what is it good for? How about switching a guitar between two amps, switching between two sound sources connected to one amp, or for reamping a signal. It can be used as a stand-alone preamp, a headphone amp for vocal monitoring, or silent guitar playing.
There's also an 1/8th inch 4 conductor jack that allows you to connect to a mobile device where it can act as either IO, or to access an app to mix in some different sounds.
The Mixing Link features a wide variety of IO connectors for such a small box. You'll find XLR ins and outs (the XLR is a combo jack), FX in and out on 1/4 inch jacks, instrument in, Aux in and out (1/8th inch) and an 1/8th inch headphone out jack. Couple this with an input gain, mix control and phones/output level along, with two routing switches and an in/out footswitch, and you have a powerhouse little box. Mixing Link also runs on a 9 volt battery or via a power supply, which you need if you intend to provide phantom power to the microphone input.
The Mixing Link has a street price of $299, and considering its many uses, is worth every penny. For more info, check out Eventide's Mixing Link page.