In Unity and GS it's fast to launch application just by pressing the Super key and typing the first letters of the app. I would like to know will Slingshot have similar behaviour.
Well, I hadn't used Super key (alone or as modifier) before trying Gnome Do and later Unity and Gnome Shell. Hitting it alone has never caused any problems for me, so I hope you consider using only Super. It is used even in Windows without problems. And in Gnome 2 and XFCE it's not used at all (or am I missing something?) We need to put it in use!
If "super + space" will launch Slingshot, then what will just "super" do?
As the Super button is generally used as a modifier key like Control it should in my personal opinion not be used by anything alone