I'm sort of skeptical that any of these will be usable as a complete replacement for a very long time. Heck, I can't even use pdflatex today because the toolcha

I'm sort of skeptical that any of these will be usable as a complete replacement for a very long time. Heck, I can't even use pdflatex today because the toolchains for several conferences and journals (I'm looking at you, Journal of Functional Programming!) require both the output to have been emitted by the latex (chokes on the PDF otherwise) and for the document sources that you provide them to also be compileable with it.