Found these when I purchased it today and tried to install it. The following are not documented in the README (or elsewhere as far as I can tell) and need to be:

1) While it’s not listed in the Requirements, you need to upgrade your Mantis install to version 1.2.8. I had 1.2.4 and had a horrible time tracking down the errors. See 0013698 for the log error you get.

2) The README implies that your should have /MantisTouch as a subdirectory under the webroot, but it works fine as the webroot itself, and this is probably what most people would want, so they can access it as http://mydomain.mobi directly.

3) There's no /favicon.ico so you probably want to add this file or else you’ll get 404 errors in the access log.

4) It's not documented that the PHP SOAP extension is required. Make sure this is installed and enabled, otherwise it won’t work and you will get this in the PHP error log:

PHP Notice: Use of undefined constant SOAP_1_2 - assumed 'SOAP_1_2' in [...]/public_html/application/models/WebService.php on line 44