From the morning blog of Buster Olney:
[...] the Braves' fan base has been responding, because of Heyward, because of the buzz about how good the team might be this year. The attendance for the second non-weekend game increased about 20,000 over what it was last year, and Schuerholz noted those, calling them a "perfect storm" of factors at play for Atlanta -- the good feelings about the team, and Heyward, and the fact that the Braves were playing the Cubs, a popular team.
"But you didn't hear from the Cubs fans [in the first two games] the way we have seen," said Schuerholz. "Usually, it's about 50-50, Cubs fans and Braves fans. That wasn't the way it was [on Monday and Wednesday]."
I was as proud of our fans as anything else during these first three games. They really came out and actually cheered (even without being prompted at times). If the team keeps winning, then the fans will keep coming out.