I am really looking forward to following Sir Larkin's Gray Box project. While I own the Gray Box, I have never used the Forgotten Realms for a campaign and have never read very much of the setting books. About the only books from the Forgotten Realms that I have used have been the various deity related books to steal specialty priest descriptions for other settings.
Even though I was a quick adopter of 2nd edition I continued to have all of my campaigns set in Greyhawk. The longest running campaign I had prior to my current 2nd edition Rise of the Runelords campaign was a 2nd edition Greyhawk campaign centered on the Temple of Elemental Evil. Until my now expired Northern Marches campaign, I had also never really done a homebrew setting. My current campaign is set Paizo's Golarion setting.
After reading Grognardia's retrospective on the Forgotten Realms and the interview with Ed Greenwood, I developed an interest in reading the grey box and went out and replaced the one I owned many years ago and also began reading Greenwood's articles about the setting from my Dragon Magazine CD.
I have been enjoying converting Golarion to 2nd edition but have, more than once, considered running my next campaign in the Forgotten Realms. The main reason I balked at using the setting in the past and still continues today is the vast amount of "canon". I am really interested in the approach that Sir Larkin is taking in his project by focusing strictly on the grey box material. If I were to use the Forgotten Realms for a campaign, I would try to do exactly the same things and the canon-lawyers would just have to gnash their teeth.