The old version fairly arbitrarily decided to prefer windows that are too
high over those that are too wide. The new version chooses the number of
columns so that all windows on the screen are as close as possible to the
desired aspect ratio. As a side effect, the layout changes much more
predictably under addition and removal of clients.
GridVariants.TallGrid behaved weird when transformed using Mirror
or Reflect. The new layout SplitGrid does away with the need for
such transformations by taking a parameter to specify horizontal
or vertical splits.
Added a module XMonad.Layouts.GridVariants, which defines layouts
Grid and TallGrid. The former is a customizable version of Grid. The latter
is a combination of Grid and Tall (see doc of the module).
