Ah, two birds with one stone!
Here are two of my friends photographed with the 16-45 @ f4.0 @ 1/125 sec @ 45mm. Not bad for the lens being wide open.
Peter, I, like many others here love my 16-45! It's very sharp, and its zoom range will cover almost everything as far as a wedding is concerned. It's a little short for a head & shoulders portrait, but for a full-length or 3/4 bridal portrait, it'll be just fine.
When you're shooting outdoors, the f4.0 aperture shouldn't matter, and when you're indoors, you'll be using flash most of the time. It has a little trouble focusing in very dim light, but when it does this, I just ask people to move to a more well lit location.
And I agree with the others who've said that the colors are very good!
16-45 @ 45mm @ f16 @ 1/4 sec.
It's a great lens, Peter; I recommend it highly.
Mike