Technically abbreviating "Christ" as "X" is actually the letter χ or "Chi". So it shouldn't be pronounced X-mas, as it's really χ-mas.

Same thing with LaTeχ, actually.

LaTeChi?

I had a Prof who insisted in pronouncing it LaTech.

The capital Chi is Χ, which is indistinguishable from X in most fonts, and even more so in handwriting.

Yes, I was using the lowercase to make it stand out.

Depends on if you intend it to be read as "Christmas" or "EX" mas. :)

Xmas is pronounced "Christmas" by most people.