I bought it first thing this morning. I'm running X3e 64 bit in Windows 8.1. I threw in a project in X3, exported all tracks as an OMF. Xchange runs in the background when you open Mixbus. You click to Open Session on the Xchange window that comes up. Locate your OMF, click open, and Mixbus opens up with all tracks in place!
This is so dead easy it's not funny.
You will be prompted when Xchange starts up to register or keep evaluating for thirty days. Click register and write down all pertinent info because you will be ask for it to register on line. Also, be sure to print out your e-mail with the order number because you will be asked for that as well. About 15 minutes later I received an e-mail from Harrison asking was I sure that I wanted to register. They wanted to make sure I had ample time with the program to be sure I wanted it. I responded that I absolutely was sold on this program and proceed with my registration.
While the registration process is somewhat convoluted, it is rather easy if you follow my instructions.
This is, in my opinion, a must have if you intend to use Mixbus with Sonar or any other DAW that exports OMF or AAF files. I don't see how they could have made it much easier to use.