Since I found out that we can't force IE 8 Browser Mode for intranet sites if "Display intranet sites in Compatibility View" mode is ticked (regardless of X-UA-COMPATIBLE headers or metatags), I'm trying to assess the impact of just running with IE 8 Compatibility View Browser Mode. (With IE 8 Standards as the Document Mode)
Can anyone advice or is there any resource somewhere that can tell me what differences there are between these 2 browser modes?
Speaking from bad experience, IE 8 compatibility mode can introduce issues with layout and page behavior. Switching versions of jQuery or CSS workarounds do not always solve the issues. This MSDN Blog post contains a good overview of IE 8 compatibility mode issues and suggested resolutions. This blog post contains more developer-centric tips beyond the MSDN post.