didn't take it, but have friends who did. Overall, they said it helped them focus their studies. I think one person actually said that they got a question that was reasonably similar to something that they watched someone else get tested on in a public mock oral.
If you need presentation prep, it might not be a bad idea, but as far as content, I'd be a little worried. Many if not most of the people who take the course are either people who feel weak about their knowledge base, or actually failed previously. Because of this, at least 2 people I can remember told me that they would end up more confused on an answer after a person who done doing a mock oral then before hand, because the person taking the mock oral gave the WRONG answer. (not their fault, but something to keep in mind.
I think you can do just as well prepping in a small group of friends. There is no substitute for having everyone give you mock oral questions every chance you can get. If you did well on mock orals at your residency, you shouldn't have a problem. If you live close to a residency program, it might be worth contacting them to see if you can take a mock oral next time their residents do theirs.