Additional information can be passed through to Google Analytics utilizing Pontiac Macros as the variable in the UTM code. This will allow dynamic information to be passed through for each impression. See the full list of macros here: Creative Macros
This will further breakdown reporting by each variable passed through the macro. One recommended use case is to implement the Seller Member ID macro as a variable for medium to evaluate exchange performance across the additional stats provided by Google Analytics such as ‘Bounce Rate’, ‘Avg session Duration’ and ‘Pages visited per session’. 
By implementing the following – &utm_medium=${SELLER_MEMBER_ID} you can view a breakdown of Pontiac traffic by each exchange through which the impressions were purchased.
For example: https://pontiac.media?utm_source=PONTIAC&utm_medium=${SELLER_MEMBER_ID}
The following would display as line items in the source/medium report and give you data for traffic by exchange ID:
‘Pontiac / 357’
‘Pontiac / 280’
‘Pontiac / 273’
These Seller Member IDs must be mapped to Pontiac Exchange IDs utilizing the the Seller Id Mapping here: Pontiac_Seller_ID_Mapping
The report above would indicate that this traffic was driven by Pontiac ads purchased through OpenX, Microsoft Advertising Exchange and Verizon Media Exchange (O&O). You can then compare the bounce rates, average session duration and more to evaluate quality of the traffic and optimize campaigns accordingly.