Marshall - 3:45 pm on Feb 2, 2012 (gmt 0)
There are many factors in a redesign that could improve traffic:
a) Crawlability which could improve SERPS
b) Ease of sharing through social networks
c) Better navigation causing visitors to look deeper and stay longer
d) Better looking, a.k.a. more inviting
That being said, how do you narrow down which factor helped or hurt.