I am not familiar with InfusionSoft, so I cannot speak to that. But for the membership levels, Organic Groups (http://drupal.org/project/og) might be your best bet.
Nancy
From: Sam Barraclough For example, a customer purchases our Bronze
Membership. They can only access content on our Drupal site that we have created for Bronze Members.
Does Drupal have the capability to differentiate
our customers based on membership level and control our content release accordingly?
And where possible we would like to link this in
with InfusionSoft API module.