Even though this thread has been slow, I thought that I would add my experience with the CPESC exam. It is not remotely comparable to the FE/PE. I attended the review class and, having worked for several years on various stormwater projects, felt very comfortable with the material presented. I spent about a week studying before the exam and made sure I knew the regulations cold. I used roak's study tips from 2009 because they were literally the only ones I could find online, and CPESC does not give you any real indication what the format of the exam will be like.
That said, I think I just about aced it. I just wish more information about the actual format of the test and the types of problems had been released. As of spring 2011, the exam is now entirely multiple choice. Everyone at my office who had taken it had essay questions or design problems, so my experience was pretty different.
Part 2 was supposed to have 6 problems of which you have to choose 3: Agriculture, Mining, Linear Construction, Small Commercial Development, Residential Development, and Forestry, with each section having 12 questions to answer. My test only had three sets of questions, so I didn't have a choice. I believe I had agriculture, linear construction, and small commercial, but they were all pretty similar types of questions with a different scenario.
I do a lot of SWPPP preparation and review, so the CPESC credential has been helpful. Even after becoming a PE, I think it verifies that you have legitimate knowledge about erosion and sediment control, so it looks good to have even if it isn't necessary in combination with a PE.