+1. I just now found out about it. Tried it, saw the tab reduced to a favicon, and will probably never use it till that's fixed. Especially with how a Gmail Tab blinks when I get a hangout message.
The "reduce to favicon" is my favorite part of pinned tabs: I pin all my slack tabs and other messaging tabs and just watch for the blue dot indicating activity and/or the red circle that indicates a private message (on slack)