This has probably been brought up before and I'm sorry if it has, but I didn't find much (beyond warnings) by searching.
The debugging in WordPress is somewhat lacking, but I don't think this is a fault of WordPress itself. The switch as it is now is fine, but it becomes a pain when plugin developers release plugins that are riddled with warnings. I can totally understand this if the plugin was built for a previous version and the warnings arise from deprecation or otherwise or even PHP version updates, but when the plugin is stated to support a certain version, then it's just frustration-inducing.
I realize that it's not easy to check each plugin for PHP warnings, but would it be possible to have some sort of requirement that plugins not throw any warnings in the version they support, either through users checking them or maybe a message on the "Upload Plugin" page?