Hi,
I have a G 5 and have used the elec shutter almost exclusively since I got it. My shots have been mostly landscapes to date so subject movement has not been an issue. It IS possible to set a sound for the shutter (wrench/spanner menu) -indeed it has 3 levels. These including silent and 2 volume levels. The sound I use is the loudest - it is still very quiet - and sounds like a classic leaf shutter. Very nice.
The elec shutter does work with the in-camera HDR feature; three exposures are taken in quick succession. So far I like the results from that, but its a very "mild" HDR.
In most all other ways this is a big upgrade to my old G3 (for sale by the way). For me what matters are the much better LCD, the automatic EVF/LCD switch, the level gauge, and of course much better ergonomics. I think the image quality is better, too, but have not really pushed it.
Cheers,
Tom