Hi there, thanks for the great plugin.
When I am working on my sites I always keep WP_DEBUG mode active so that I can ensure my own code is not generating any errors and that it is all valid and logical. Unfortunately PowerPress causes many notices to be thrown that end up showing all over the admin and can end up interrupting the flow of pages when they are shown before a redirect.
It would be great if you could try to clean up some of these notices in the next version. They are always simple fixes and usually the result is to clean up your code and make it more logical. This Codex covers the debug mode in detail:
One thing I noticed in the code itself is that in many cases you use the @ sign when checking variables to suppress errors. This does not stop WP_DEBUG from showing the errors, so any use of @ in your code would be a good place to start looking for WP_DEBUG issues.
Thanks for considering this request :)