I'd try them at the range. What the heck.

First thing that comes to mind would be noise. They look like something that would whistle on the way to the target.
Speaking of Turbo Nok, not sure if you guys saw this yet. It's from over at ArcheryTalk.
http://www.archerytalk.com/vb/attachment.php?attachmentid=89541&stc=1