5.Qxd4 works fine, doesn't it?
If Black chooses to take away my bishop pair via Nxc4, I grab back my Gambit pawn with Qxc4 and unless I'm completely blind, I have Q + N and a pawn out with "nothing" for black. That's all the initiative white could ask for in an opening such as this :)
Now Black could get fancier with ideas like 5...Qf6 but I still believe that White is quite happy.
I am completely changing my repetoire and need to clean up some things. Can someone please refute this?