So I ordered the PS3 to Xbox One Brook converter right after the new year during FocusAttack's quarterly sale. I got it on Jan 11 because I got the slow cheap shipping and they got quite the backlog of orders during the sale.
In order for it to work with the MC Cthulhu PCB, it needed a firmware upgrade. I knew this going in as I looked it up on the SRK boards before ordering. However, it bricked during the upgrade. I emailed Brook's support and got no response. I contacted them via Facebook and they would only respond with questions asking me if I followed the directions (which I did).
After about 2 weeks of getting nowhere with Brook's support, I contacted FocusAttack. I asked for a replacement but they requested that I talk to their tech support first. After a week of getting nowhere with their tech support I asked for a replacement. To their credit, they did reach out to their Brook contacts but didn't have any better luck than I did.
I got the replacement today and successfully updated the firmware! Though it was not without difficulty. The firmware upgrade has two files. During the installation of the first file, the firmware upgrade failed. I had to reboot my computer and flash it 3 more times before it started behaving and acting as intended. The second file installation went off without a hitch (this is where my first one bricked).
But now I have a fully functioning arcade stick for my Xbox One. Now to relearn Killer Instinct and MK X! When I get a PS4, I'll likely get the PS3 to PS4 converter and switch them out as needed.

It is a great little device but the firmware upgrades sure are touch and go. Brook's support is downright awful. If you get one of these, be sure that the place you are buying it from has good customer service and will accept returns.