At the same time as writing my previous post I discovered a youtube video with the same name as this blog and an accompanying thread at DPReview. For my goal here is to collect as many technical tips I'm re-posting it:
The corresponding DPReview thread can be found here: http://forums.dpreview.com/forums/post/50521335
Personally, my findings from this video are that Quick Menu can be customized (separately for each mode) and that electronic shutter is limited to ISO1600 and 1 second shutter speed. Good to know.
Some comments to the viewfinder smearing issue: I don't have it. At all. In fact, my old GH1 has much fuzzier viewfinder image than GH3. I bought my GH3 in a shop in Europe though, can it be that smearing is a US-specific quality control issue at Panasonic? Neither I have the flash sensor issue.