I emailed Andrew at Studio Six Digital and asked about the switch on/off noise through the iAudioInterface. I also asked about the 'missing' mic clip. His reply is copied below.
"The output noise glitch problem is due to Apple requiring that we shut down audio power when not in use. So yes it is power saving, but they won't let us get around it.
We did not end up including the mic clamps, these work well:
http://www.bhphotovideo.com/c/product/1 ... phone.html"
Dominic