Two comments (I was just burned by this J):
1. the environment.plist file is only read AT LOGIN. Therefore, after creating the file, you have to log out and log back in (no need to restart).
2. on MacOS X 10.5 (Leopard) and earlier versions, this file is read only if the app (i.e. ST2 in this case) is started from the Finder (or, I suppose, the Dock); it is NOT read if it is started from Spotlight. On MacOS X 10.6 (Snow Leopard), this is not a problem: things work even if you run the app from Spotlight.
Just thought I'd share