Took the exam yesterday, I have been using XP for 7 years, spent 6 weeks studying, read 70-270 second edition, used CBT Nuggets and Testout.
Working toward the MCSA in reverse order, and completed the 290, then 291 and finally 270, having already obtained NET + and A+, so MCSA is complete.
Just ordered the Security + book and plan on working toward that one next since it is a lifetime certification if completed prior to 12/31.

Plan on taking a week or two off in the mean time.