I am considering trying out ConTeXt, XeTeX, and LuaTeX, but one concern of mine is the fact that I am using a large number of LaTeX packages.
What I am especially interested in is the functionality I presently get. Put in the simplest possible terms: The large number of LaTeX packages exists because they provide valuable functionality. It would seem hard to believe that ConTeXt is so advanced that all of these packages' functionality is not needed within ConTeXt. Similarly, I am wondering about present-day compatibility of LaTeX packages with XeTeX and LuaTeX.
So, how much LaTeX functionality is easily available or needed in each of ConTeXt, XeTeX, and LuaTeX, and how do I make it available?