Currently for the MCM SQL Server 2008 Knowledge Exam, there is a built in delay in the test taker getting their results. This is due to the fact that the exam was listed as Beta during publishing to Prometric. There is then a once a month rescored that occurs, with your results being sent to you in the mail.
This will change for the MCSM: Data Platform Knowledge exam (88-986). We cannot change it for the current MCM Exam 88-970.
Now you can expect to receive your Lab exam results in around 5 business days (or less when possible).