As pointed out in the homily, this section is often used as an explanation for "deathbed" conversions. People are often frustrated that they spent all of their lives trying to be good in hopes of deserving their place in heaven while others might have filled their lives with decadence only to convert at the last moment and yet still get the same reward. Those who want to "game" God's system argue that this encourages people to ignore God's teachings until they are about to die (like Tom Walker attempts to do in Washington Irving's "The Devil and Tom Walker"). However, I think that Jesus was making a different point.
While He was certainly warning against envy of others as our pastor pointed out, Jesus is also making a statement about pride. The landowner intentionally pays those who were working all day last. He had them wait the longest while also making certain that they saw how the others were treated. Jesus even ends the parable with the line He often repeats: "Thus, the last will be first, and the first will be last." He was warning His disciples (and us) about feeling superior to others because of our accomplishments. The laborers in the story were like Jesus' disciples who were arguing over who would be greater in heaver; they felt as though they deserved some sort of special treatment because of their closeness to Jesus. Instead, Jesus teaches them the importance of humility as well as the need to be thankful for what one has been given.
I need to work on my own envy and pride, for I certainly suffer from both of those afflictions.