PV2012 utilizes autohighlight recovery, which is why the Exposure control behaves differently than with PV2010.
The PV2012 Exposure control is used to initially set the "midtone" areas in a "top-down" adjustment flow. See #2 instructions at this link:
http://forums.adobe.com/message/5075641#5075641
There are numerous PV2012 tutorials in this forum, here's one: