No, no, always glad to spout off to someone!
What I done was: When I saw there were still places on the workshop, I sent in the form with a cheque for the money, and then when I was contacted to say that I had a place, I was given the information about uploading my dummy book to an online file sharing service so that the people running it could see it and comment before the workshop day itself. That was pretty much it, although I did revise my book between getting the comments and the workshop day.
Comments from the organisers were meant to be tough but fair. I found them very helpful, and I didn't get the vibe from other people that anything horrible had been said.
Comments from other participants were also fair - we were all in the same boat, and appreciated how much effort had gone into creating the dummies, and while pointing out weaker areas, were constructive criticisms. People might write that they thought, say, the plotline was confused at a particular stage of a story, but no-one scribbled abusive notes to anyone!
A dummy is a pencil rough - fairly detailed but can be sketchy, including the text in the layout. Usually the author will do a couple of colour spreads as well, so that a publisher can get an idea of the final product. Some people had made theirs into actual book-shaped things - mine was a pile of photocopies!
There was quite a range within both illustrations and stories. I would say that not all were at what I would think of as a 'professional' level of illustration, but even so there were good things and ideas in all of them.