Lag - delay about a second between clicking the shortcut and action.
Double-clicking the taskbar - I have had this option enabled, but never had a free space to use it.
With "Reserve empty space on taskbar" option it's great stuff. Thank you.  

Thank you for hint. I tried to make a link and pinned it to taskbar but there was a lag.

The way with Quick Launch bar from your link is better but there is vertical lines on the sides of the button.

So the request is actual. It would be good to add some tiny button half the width of the standard shortcut.