I've been working with the reference checkout now for 5 or 6 months, and feel I have a pretty good grasp of how things work. By far the most common request I get is to set up analytics, particularly third-party conversion tracking systems like Adwords, Adroll, Adlucent, Barilliance, etc.  Generally speaking, there are 2 use case scenarios for tracking during the reference checkout:

1.  Google analytics mode - These tend to be traditional analytics systems that expect to have the script loaded as soon as possible, then track things like page views or events by calling their proprietary JavaScript functions in the code of the page. It is expected that the script will load on every page during checkout, With a variety of function calls used depending on the situation. For example, you might track a pageview and  an event  on the login/register page,  and track a pageview and transaction  on the order confirmation page.  This is the scenario NetSuite has designed the