I bought Lumin D1 replacing NAD M51 + Squeezebox for my office setup.
I am happy with the SQ improvement and Lumin app is much better than Squeezebox app or Marantz app.
I updated Lumin application on my Ipad1 (1st gen) several times without a problem.
But the last update available on Apple Store doesn't work well with my Ipad1.
Lumin app always crash within seconds. I did try to reboot the Ipad and also uninstall /re-install the app but get the same problem. It seems Ipad1 doesn't have enough resources to run latest version of Lumin app. So if you are still using Ipad1, you may get the same problem.
But if you use Ipad2 onward it should be fine.
I just send an email to Lumin, hopefully they have a solution. Temporary solution is rollback to previous version but unfortunately previous version of Lumin app is no longer available in Apple Store.