CiviXero - what's the status?
The Issue list for the extension is at https://github.com/eileenmcnaughton/nz.co.fuzion.civixero/issues and is the logical place for 1) bug reports, 2) feature requests, 3) bug reports re: performance, 4) feature requests/bug reports re membership purchases. You can probably also use that issue queue to ask 5) about how it is implemented, or even better, offer to update the documentation if provided with that answer.