This is my completely biased review on the difficulty of the tests in the MCITP track, based on nothing but my personal experience and perceptions at the time of testing. Your testing experience will most assuredly vary, so don't take my word for it.
So far, I have yet to fail a single test. So there's that, too.
In the order of easiest to most difficult:
- 686: I do not know if it was the prep material I used (Measureup + Sybex) or the age of the test, but this one was a breeze. Study the Measureup and the Sybex book and you should do fine.
- 647: Yes, 647. I found it easy as well.. probably because a) I'm good at planning and b) I'd been through all of it before on every other test.
- 685: Pretty easy. There was some new material on there, but nothing major.
- 642: I would not call this one easy, but it was not hard either.
- 680: As an all-encompassing OS, it was harder than the other Win 7 tests.
- 640: My first test in Iraq. Testing center issues made the experience harder than it had to be. 6 hour wait to take the test. Ouch.
- 643: One of two tests I thought I might fail. I didn't, but the margin was smaller than I would have liked. Then again, my experience with Sharepoint is nil beyond labs.
- 646: The first 2008 test I took, and by far the hardest. Though being first, I did not have the benefit of having studied the material over and over again.