I always tell people to do exams during Second Shot season.
Reason being – it makes the first one a practice. Don't bother studying, don't bother stressing, just go and see how you do. Then you can sit it a second time for real.
Feel like giving it a go? Register at http://www.microsoft.com/learning/mcp/offers/secondshot/default.mspx before booking.
Looking for more? Well, the SQL 2008 exams won't be around for a while, but there are a lot of other options out there.