i don’t know if it’s a TikZ or a ConTeXt bug, but with the newest mkiv beta
installed with mtx-update.lua, tikz fails when using the option “text badly
centered” in combination with “text width”:

\usemodule[tikz]
\starttext
\tikz\node[text badly centered, text width=1cm]{fail};
\stoptext

gives:

\tikz@text@action ...p =0pt\rightskip \@flushglue
                                                  \leftskip \@flushglue
\relax
...

as it doesn’t occur with LaTeX, i think it might be a ConteXt bug.