Tested upgrading my browser from Firefox 3.5 to Firefox 3.6, found that it launched but just gave me an empty blank white window (no browser controls). Long story short, I had used this profile with trunk when testing the D2D goodness. Seeing as how we're telling people to set this pref to try D2D on trunk, and that people commonly use the same profile with different versions (even though we're kind of ambiguous about that being supported or not), we should have the 1.9.2 code ignore this pref, or only accept known-good values to prevent this from being a footgun.

Justin, try Firefox 3.6.2 because bug 549668 was landed on 1.9.2 tree.

The dupe shows as 1.9.2.2-fixed - can we confirm?