I have gotten the MK view both times I stayed in the Atrium Club (September 2006 and June 2007), but I faxed a room request 4 days prior to check-in each time. I have been faxing reasonable room requests (but not upgrade requests) since I first got hooked on Disney in 1993, and so far, it has worked every time.

(I have not heard of a way to do this by e-mail. CRO requests usually work by themselves, but the fax seems to improve the odds.) Since Atrium Club can be either side of the building, it's perfectly reasonable to fax a letter to the Disney Room Scheduler, explaining and requesting what you want, with the details of your reservations. Bay Lake is wonderful, but the MK side has the Wishes fireworks from your balcony. That is so amazing. And, if this is your 1st time since the room renovations last year, you will be thrilled with how beautiful the rooms have become.

This is the letter I sent in September:
(407)824-3539 (the fax number)
September 18, 2006
Dear Contemporary Resort Room Scheduler,
My party and I have a room request for our 6-night Concierge stay from September 21 through September 27. Our reservation number is ____________, under my name, ________. The reason we chose the Contemporary this trip is because of the amazing view of Wishes fireworks. We request a Magic Kingdom so that we can enjoy them with our children.
Thank You, and Have a Magical Day,
name
address
number