I have recently been the 'official' photographer at my brother in law's wedding and whilst I did get some nice shots, I would not go as far as to say they came close to professional shots. I was so nervous that most of the recently acquired information (I've learnt that theory and practise are worlds apart) stayed right in the back of my head...
My legs were like jelly the next day, as I was not used to squatting at a rate of once a minute for six hours. I ended up with loads of pictures of people I knew and a lot less of people I didn't, which would be something that would not happen if an independent professional had done the job.
I am in two of the 847 pictures taken with my camera and the person that took those did not know how to frame it, so he cut my left arm off in both of them...
Not ideal, but the good thing is that by desperately hunting for info on how to shoot a wedding on the www I found this place.
http://sallyandpeter.blogspot.com