Just a quick note if you happen to use the ajax module. By default, that module includes a packed version of the jQuery Form Plugin. This is in ajax.module, in the ajax_preprocess_page() function near the very top. Since this is a packed JS file, when it is aggregated with other JS files by advagg it can cause strange and subtle compatibility issues that require lots of time to debug.
I opened a ticket in the ajax issue queue with a patch, but to save time for someone else I thought I'd open an issue here as well. Feel free to close this or link it in the docs. #1867284: Do not use packed Javascript file
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mikeytown2 CreditAttribution: mikeytown2 commentedAdded that issue to the module page