I took the exam a week ago and passed it with the score of 900. It was quite comprehensive exam with 43 questions. Transcender is useful but extra study should be done. There were many very specific questions, so working knowledge of TFS is a big plus. Exam 70-510 is for TFS 2005 and I am not sure if and when Exam for TFS 2008 will be released.
Good starting point: http://www.microsoft.com/learning/exams/70-510.mspx