The Luma ExponBlur tool actually had some buggy channels being added to your scripts (something leftover from the nuke 6 days I think). I cleaned these channels up so it will not add unnecessary bugs or channels.
or you guys can go straight to the source here:
http://www.nukepedia.com/gizmos/filter/l_exponblur
This is my Feather Gizmo, I will put it on nukepedia soon:
More will come!
Cheers,
Tony
Compositing Mentor 
Just would like to say that I’m really enjoying this series of tutorials about keying you’re doing… they are great! Can’t wait to see what is coming up next… 🙂
regards!