Hi,
the behavior of \vfill has changed in the latest beta. In some of my setups, I used code like this to produce vertically centered content:
\starttext
\null\vfill
vertically centered?
\vfill\null
\stoptext
This works with the beta of 2015.11.19 19:13, but no longer with 2015.12.21 12:16. Not sure if intended, side effect, or bug?
Thomas