Took the Advanced Admin Certification test today (and passed!) but I must say it was a trying experience! During the exam the Internet connection at the testing center went down a couple times, the last time causing the instructor to have to log back into my test with only two questions left. I couldn't help but to think that I was going to have to redo the test the entire time he was setting everything back up. Also, I fortunately didn't use the entire allotted 90 minutes, as each time the connection was down, the timer was still counting against me.
Overall the test was as expected, many nitty-gritty questions on which editions certain features could be used in, a handful of questions on Ideas, and then of course security. I was surprised at the overlap between the Developer test and the Advanced Admin test, I would say maybe 25% or so was in both tests. Regardless, with a little study time, the test is totally doable!
Good luck on your exam!
UDATED 6/20/2012: The flash cards for studying that I referenced in the original post are no longer available, however a quick Google search revealed many other sites available that provide similar information to help prepare for the Adv. Admin test.