> On the other hand, from my brief number of ASL lessons (about a years worth taken as an adult in my mid 20s) the facial expressiveness inherent to ASL gives it something hearing people don't get in normal conversation. But to me that's a pretty small benefit compared to the things a deaf person is missing.

I don't know ASL, so can you elaborate on this? Aren't facial expressions just as important for non-deaf people?

Facial expressions were mandatory in ASL, at least according to my teacher. The best analogy I can think of is of a tonal language, where raised eyebrows, a somewhat astonished look, or a frown with a furrowed brow are the tones.