I think this is a pretty good use of flash. I would like to see it positioned a bit higher. The camera too could have been a bit higher. And a longer focal legnth.
With the flash higher, the shadows would fall lower rather than directly to the left. Raising the camera would have put the horizon line out of view. A longer lens would have helped with the groom being slightly dwarfed.
But mostly, the bride could be posed differently. Getting her feet and the gown out from under her and going off to the left whould help. Also pose her right hand with the bouquet further out and away. And getting the groom up higher, maybe on one knee, would move his head higher in the frame so their eyes are not on the same level.
And, as Ls3D said, that black, cylender thing is doing nothing good.
-Pete