I gave it a try during the free trial. I didn't like that it started from the beginning, but that was great to get me re-focused and back to basics.
And it showed me that I'm my own worst critic. The self-rating thing was almost laughable. I also did my annual review at work at that time. I really am way better than "average", but I rarely rate myself any higher than the middle grade/choice. I even wrote a blog about it. www.sparkpeople.com/mypage_public_journal_
Spark Coach is a great tool for folks new to Spark or who need some extra guidance, but I'm fine with what Spark offers on the regular site.