yeah, I know about the slush piles and some tricks around them. Getting a good agent, from what I've heard from some published authors, is a Russian roulette game. Most are not able to deliver or are all talk and no walk. A good one usually deals with already established clients.
My experience, so far, has been to ask published authors and attend a couple of workshops and seminars. I spoke with Stephen King's first publisher/editor (who is a well published author himself) and he had some very good reasons for seeing a book doctor for your first time out. He did like what he saw when he looked at the first 9 pages of my story, though. A book doc is good for if you don't know the details that publishers look for to reject you, and apparently there are a lot of little reasons. And their motivation behind is always to give you good advice that helps get you published. If they were a fraud or waste of money, then their clients would be unpublished. You get published, they get more rep and then more clients.
Personally, I will try to find an agent. To me, it's like buying a house with a realtor to work for you. They know more about the tricks and legalities than yours truly. Hopefully, they even know the people I would be trying to get to publish my book. I'll also try to get it published for a while without a book doc, but if that fails, I may try to get one to look it over for me.