Wow!! What a DIFFERENCE this makes for our visitors!
After upgrading to XenForo v2.1 many of our visitors started complaining that the logon dialog/page could take as many as 20 second to display. That was insane! It turned out that XF v2.1 adds a 30,000+ common words dictionary to the logon page. It's nearly a megabyte! ... and it was badly clogging up our logon process.
This beautiful little AndyB AddOn restores our forum's previous fast login... which really matters! Thanks, Andy!!