It only partially works with my iPhone 5s and iPad Air. iPad -> iPhone shows the Safari icon on the bottom of the iPhone screen, but opening it doesn't actually bring up the active web page from the iPad. iPhone -> iPad does not work.
None of it works with my 2010 iMac, which is apparently (and sadly) to be expected. I'll have to try it with my mid-2011 MacBook Air, which is supposed to support it.