I wanted to be able to watch mlb.tv games in full screen without using Mosaic. Mosaic seems to hog a lot of memory and makes it difficult to do other things while I keep the Indians in the background.
From Lifehacker I discovered you can zoom in at pretty good resolution using the Control button and the trackpad (or mouse-wheel, I believe).
Zooming-in on the regular mlb.tv feed yields a pretty good fullscreen that is easy to get out of.
Watch out, though, if you zoom in too far you might get Pronked.
If there are better ways of achieving fullscreen, please let me know.