It is quite obvious that landing this in Ubuntu would clearly have "a severe impact on a large portion of Ubuntu users" and also "severely affect applications beyond the package responsible for the root cause".
After all Compiz is a window manager and users expect correct window management from it, especially no regressions there and *every application with deco* is now affected by the shrinking, so IMHO this bug is really a showstopper...
Regarding the "Critical" status:
It is quite obvious that landing this in Ubuntu would clearly have "a severe impact on a large portion of Ubuntu users" and also "severely affect applications beyond the package responsible for the root cause".
After all Compiz is a window manager and users expect correct window management from it, especially no regressions there and *every application with deco* is now affected by the shrinking, so IMHO this bug is really a showstopper...