Had a very nice e-mail exchange with Shane Woodson at iFly. When viewing the absolute altitude of a target, the target's indicated altitude should be quite accurate. When viewing the relative altitude of a target (by invoking the relative altitude mode via the Settings>Alerts and Warnings menu), iFly uses your GPS altitude to calculate the relative altitude. Was told this was the best compromise. As such, when viewing a target's relative altitude it is only accurate when your GPS altitude matches your actual altitude. (Does not happen very often, could be 200-300' or more different).
My kudos to iFly. They REALLY take the time to answer your question!!! Thanks, Shane.
BUT the warning as stated in the preceeding post says..... Ensure there is a LOT of separation. We must STILL "See and Avoid"