Dear Hans,

I noticed a difference between mkii and mkiv in the behavior of \mframed: it seems that in mkiv the frame is not vertically aligned with the the + sign in the following example (or rather it is not vertically centered, please see the attached PDF produced with ConTeXt  ver: 2013.10.15 13:52 MKIV). 
Does one have to use now a new key to require this sort of alignment?

Best regard: OK

%%%% begin mframed-example.tex
\setupcolors[state=start]

\def\graymath{\mframed[frame=off,
   background=color,
   backgroundcolor=lightgray,
   backgroundoffset=2pt
   ]}

\starttext

Since for $|x| < 1$ we have
\startformula
\log(1+x) = \graymath{x- \displaystyle{x^2\over2}} + {x^3 \over 3} + \cdots
\stopformula
we may write $\log(1+x) = x + O(x^2)$.

\stoptext
%%%% end mframed-example.tex