I just installed ACR 7.1 RC on a Windows 7 Professional 64 bit system and identified an issue relative to how ACR 7.0 works. When I select an image that was initially converted using PV2010 (CS5) and click on the "!" on the image to change it to PV2012, make a few adjustments in the Basic panel and then click on the "3 ---" and select "image settings" it changes back to PV2010 with all the settings, but if I then click on the "3---" again to switch back to PV2012 with the settings I made it's already setting in "Custom Settings" and you can't switch between PV2010 and PV2012 using this approach.
If you have any other panel than "Basic" selected it allows you to switch between PV2010 and PV2012 by selecting "Image Settings" or "Custom Settings". You can also switch between PV2010 and PV2012 in the "Basic" panel using this approach if you don't make any changes to the initial PV2012 slider settings.
ACR 7 does not have this characteristic.
I have found that if you change to something other than the Basic Panel and then click on "Image Settings" it works correctly - you can switch between "Image Settings" and "Custom Settings" and you can even change back to the Basic Panel and it also works correctly. If you click on "Image Settings" for the first time while in the Basic Panel, the "Image Settings" become "Custom Settings" and you lose the adjustments you made after you clicked to update to PV2012.
I did not have this problem with ACR 7, just ACR 7.1RC.
I have returned to ACR 7.0 and it does not have the issue described above for ACR 7.1 RC. I am reprocessing images that were already processed with PV2010 and switch between PV2010 version and PV2012 version using the "Image Settings" and "Custom Settings" . I can do this in ACR 7.0 while in the Basic Panel, but not in ACR 7.1RC. In ACR 7.1RC I have to switch to something other than the Basic Panel before I switch between PV2012 and PV2010 using "Image Settings" and "Custom Settings", but after I do this one time for an image I can then do this in the Basic Panel.
This bug needs fixing before the production release.