Performance should not be noticeably different.  Remember that basically all the feature does is click the "Verify My ID" button for you, saving you the trouble of that extra click, and allowing you to continue working while the ID is loaded.  Other than that the process works basically the same as if you'd clicked the button yourself.  The ID image is still in the same place it was before, and the system still has to go and find it and pull it back for you to view.