A common scenario we find ourselves in is to have a parallel composition container with a single child step that operates on a given fileset matching a pattern -- In one specific case, this results in the build step being executed roughly 470 times.
In cases where we need to cancel or stop a build in progress that has begun processing these repeated build steps, the cancel never seems to work as expected. After clicking the "stop" button, it will stop processing all steps that are currently "running", but it will not prevent any other steps in the queue from being processed.
The build step's execution conditions are "as long as the build is not canceled", and it works as expected when we use a sequential composition container. This makes it nearly impossible to cancel the build in any sort of timely manner, as it requires someone to sit there and click cancel every 5-10 seconds for about 5 minutes before everything's really canceled.