Just a random afternoon thought for you...
I can think of two cases in the past in which a playoff-bound Cubs team fell flat on their faces after reaching the NLDS. I'm talking about the '07 team, and the '98 squad. Both teams limped into October.
I'd like to create a hypothesis about the likelihood of post season success for teams that clinch in the last week of the season, as compared with teams that clinch earlier than that, but I haven't had the time to do research. However, I suspect that it'll be much ado about nothing.
But if it isn't, then the Cubs being the first to clinch in the NL might be a happy little advantage. At this point, we're almost guaranteed that whichever team the Cubs play next week, it'll be a team that didn't get in until the bitter end. That means that their regulars won't be as well rested, their starting pitchers will have been run harder, and hopefully a little bit of that competitive fire that got them into the playoffs will have burned out.
Just a thought while we wait for the Cubs to beat the Mets tonight.