I love this option. I found that a few months back and just like you I could not wait to come and share it. It is kind of like your birthday each time you find a good useful trick isn't it?

Hmm, after reading that article and looking back on some shoots I've done, I really could have used this. 
A BIG feature would have been the ability to override the autofocus.  Especially when I was trying to capture a dragonfly in mid flight.  I was constantly switching between manual and auto.  He'd land and I'd auto focus on that, then I'd have to switch to mf.  In doing so, many times I bumped the camera and the dragonfly would go out of the frame.   Very useful tool for shooting wildlife.  Many times I just want the eye or part of the head in focus.  But I can use af to get part of the head in focus, then fine tune wiht manual. 
Everytime I've seen this come up, I've really just dismissed it until now.

I like having the option, but I like the setup where if you hold the back button it won't focus a lot more. That way, if I'm already in focus, I hold back while I hit the shutter to actually release it.

I didn't want to revive this topic, but I had to say thank you to the OP!! Since this morning I thought my 50mm 1.4 lens was damaged for sure. I swear I don't remember going to the  Custom Functions (C.Fn) or hitting anything on my camera but it was not AF on any manual mode and I thought it was malfunctioning. There is a Canon Factory down the street (literally), I'm like trying to gather up my kids and go down there and try and figure out what's going on and etc. .... I had been grumpy all day lol and I just happened to come to t2iforum and search for a solution and found this thread! Man I am so relieved. The power of reading and researching. I love this site!!!!!!!!!!

Oh and to the mods, I surely won't do this again if it was a no-no but man I had to post some type of gratitude

I turned this function back on because your bump reminded me I stopped using it and really really should start again.
I also MUST get Magic Lantern sorted soon too!

hey guys, just changed settings and it works well. Might sound like a silly question but will the auto tracking still work with any canon telephoto lens using back-button focusing? Cheers.

Just want to thank you guys for this thread.  I've been using BBF for a couple weeks now, and it's like second nature.  I'll never go back!