Currently, only daily uniques are available for eVars in Report Builder. Unique Visitors should be available just like they are in the web interface. Thanks!
Thanks Eric. Yes, UV's are available under the "Traffic" metrics, but it would be great if they were in the "Coversion" metrics so you could build one table with multiple metrics including UV's. Currently, you would have to build two tables using the same dimension to get your events and UV's in a workbook. This is not the case when working within the UI.
Report Buider supports the ability to mix unique visitors with conversion metrics,