I sat for the 70-642 today and passed on my first attempt

. You really need to know your details to get through this one.
I used:
- MCTS: Windows Server 2008 R2 Complete Study Guide
- MS Press 70-642 (1st edition)
- Labsim practice exams
- Virtualized Labs
I studied for this exam and the 70-680 over the last 2 months and found the material complimented each other a bit (5-10% overlap).
I am sitting for the 70-680 Friday.