As far as I understand it (a few days of research here and there), there are two major TeX engines: pdfTeX and XeTeX. pdfTeX is the "standard", having been around since the early 1990s, renders straight to PDF, and improves on some minor formatting issues with original TeX.
XeTeX, on the other hand, also outputs PDF, can use any system font without complication, and can accept Unicode input by default. And yet for some reason it's not the default engine in any of the TeX distributions.
Do I have this right? Why is pdfTeX still the standard? Which do you use?
I use whatever texlive releases and Debian / Ubuntu package for my respective systems :) It seems there is a texlive-xetex package but I haven't used that yet.
More seriously, (La)TeX is now a standard and these things do not change overnight. And I am quite frankly quite happy with pdftex --- in no small measure because it can render latex files I have written over two decades (modulo the latex2e change of yore).