As the title suggests. I tried on FFx Nightly and Opera v12.1. Fullscreen works fine, but the quality is reduced compared to the previous version of Flash Player v11.2.

Example link: http://http://www.justin.tv/420nomad466 or basically any video on justin.tv or funnyordie. YouTube videos work fine in both modes!

Flash Player 11.4 (Pepper Flash) on Chrome works fine in both windowed and fullscreen modes.