So I finally had a chance to try out my K-SOURCE clipons the last few days. Just for reference, I used CIPA clipons on my 2010 Silverado.
Not much to add to duke3k's assessment. They work just fine, quite comparable to the CIPAs only easier to install and look a little more OEM than the CIPAs.
I did notice one was vibrating a little. I took it off and saw that there is an adjustment screw (phillips) on the ball and sock (easily accessible). Tightened it a little and problem fixed.
Full blown OEM trailering mirrors would be nice, but $52 vs ~$800 it's an easy choice. Plus I don't have to put up with the blindspot %100 of the time.