For example, if 'vnc' is set in the system's kernel options and '!vnc' is set in the recipe's kernel options, 'vnc' should be removed. But it's not. We are calling InstallOptions.combine_with too early, so the ! options from the recipe were being discarded.
On Gerrit: http://gerrit.beaker-project.org/1094
Beaker 0.9.0 has been released.