I have to admit that I find the plotmath expressions in R a little fiddly to annotate plots with mathematical notation.
Apparently I am not the only one, but Stefano Meschiari did actually something about it. A few days ago his package latex2exp appeared on CRAN.
The package provides the wonderful function latex2exp that translates LaTeX code into plotmath expressions. Brillant! All I have to remember is to escape the “"