We've released an update to ProEXR that contains performance improvements, minor bug fixes, and enhancements to the After Effects Comp Creator. Everyone should go get it.
Probably my favorite feature, however, is a new report that you'll find in Photoshop's File Info dialog. Look in the Description field and you'll see a complete breakdown of all the channels and custom attributes included in the EXR. For those of us that can get files from a variety of places, it can be very interesting/useful to see exactly what's in a file. For example, some of the ILM Sample Files contain information like aperture, altitude, latitude, and longitude.
Since this report can get a little long in Photoshop CS3 and earlier, I've made a Custom File Info Panel that fills up the whole dialog with it. Download it here and drop it into the Custom File Info Panels folder:
/Library/Application Support/Adobe/XMP/Custom File Info Panels/
C:\Program Files\Common Files\Adobe\XMP\Custom File Info Panels\
Currently there is no way to save your own custom attributes in an EXR, but options for doing so could be explored if there is interest from users.
Incidentally, we've done some benchmarking recently and our tests have shown the After Effects plug-ins to be somewhat faster than Adobe's included OpenEXR plug-in. This can mostly be attributed to ProEXR providing a native AE plug-in, while the Adobe plug-in is actually made for Photoshop. So yet another reason to switch to ProEXR.