According to the MLS Fact and Record Book, there will be a shift in the playoff format for the 2008 season. Eight teams will still get in but this year the top three teams in each conference are guaranteed of a spot. After the top three from each conference, the two teams with the most points will go regardless of conference.
It's a slight shift from last year when the top two in each conference were guaranteed a spot followed by the four teams with the most points. The format allowed the Kansas City Wizards to get in as the four seed in the West as they finished even with Chicago with 40 points but lost out on the tiebreaker. Under the previous system, Colorado would have gotten in with 35 points.
It's a minimal change, but a change nonetheless. It would not have affected last year's playoffs, for instance.