New versus Returning Visitors Report

Hm, based on what Unique Visitor metric?

If we want conversion events in that report, it would be the "Visitors" metric :-/

Cookie lifetime?

A new unique visitor (cookie) is only new one time.  The sense of "newness" should not be configurable.

If it's a new/repeat visitor report, the report should look at the cookie lifetime. 

Other milestones, like someone coming back in the last 60 days, are related to loyalty and engagement, not newness.

I absolutely agree.  See my ticket 120410-000127.  We want to be able to look at monthly unique visitors & say how many were cookies seen for the first time this month vs. a repeat from past months.  And then do the same on daily, weekly, etc.  Any time frame.  This should be a standard site catalyst report.  We want to understand what % of VISITORS are brand NEW for each time frame.