Give it a try! Now that I have used it I don't think I will ever go back. This is not a paid endorsement.
[Editor's note: GLTerm uses OpenGL to render a predefined selection of font sizes very very quickly. I tried it, and it's definitely FAST. However, I've gotten used to my semi-transparent terminal, and would find it difficult to give up this (trivial yet valuable to me) feature. GLTerm does not currently offer transparency (a future update, perhaps?), but it is incredibly fast and well worth a look.]

