Seems like a great feature, except I can't seem to get it to work.
You have to set your User IR folder in the preferences (otherwise the user browser shows just a blank folder). But while it will let me browse my IR wav files, every time I try and load one of them I get a File Not Found message in the slot where it should show the file name.
Perhaps it doesn't like Windows file paths with spaces? The same wav files can be imported using the Import IR, so I'm not sure the problem is the file itself.
If this does ever work I think it would mean 3rd party IR presets become practical. Which would be a huge win. I know I setup a couple using IR files I had but gave up given how much work it was to import the IR, setup the preset, etc.