[luatex] otf fonts (ligatures, cache, etc.)

[Karl Berry]

    for example 1/4 (I'm sure there are more pertinent examples 

For example, "ffi" and "ffl" are standard ligatures in English.

    Also, how should I handle font cache? For example when I ask to load the 
    same font (with same options) with different size, 

I was curious about that particular case myself.  Does OpenType have any
concept of non-linear scaling?  Can SomeFont.otf give a
differently-designed result when loaded at 5pt than 10pt, a la cmr5
vs. cmr10?  Or does it have to be two different otf files?