Maximizing the game window (e.g. to 1920 x 1174 on a 17" MacBook Pro), then entering into fullscreen mode and exiting fullscreen mode results in the game window having its previous/default dimensions (854 x 502). The game should remember the window size and switch to that size when exiting out of fullscreen mode. That is how it previously worked (pre-1.6).
Confirmed with Win7-64 / Java 7U25