I agree after switching from my 2011 MBP to a Retina I was sad the IR remote would no longer work
Although your iPhone/iPod Touch can be used as a remote, it's tedious to get to it quickly and also it will only work for iTunes. I often use spotify, and if my 2011 MBP had Spotify open and playing when I would walk away to listen to music, my IR remote would still control Spotify since it was left open. I can no longer do this with my Retina, so I've been looking for a remote as well.
This remote should work, though I can't say I've tried it yet. I actually originally bookmarked the bluetooth remote to use it with a bluetooth adapter in my car, but I haven't gotten around to making my car bluetooth compatible yet so I haven't used the remote. I've read a lot of good reviews on it, though, and I'd imagine it would work for iTunes as well as other applications on your Retina.