I have not used them personally, but they look pretty nice. There is a video in the "Knifemaking Tuesdays" video series where John uses one (actually, I think he has used them multiple times).
Here is the video, should start with him loading the plate he is surfacing, if not, fast forward to 1:29 in the video.
[video=youtube_share;cdiFm4yA6z8]http://youtu.be/cdiFm4yA6z8?t=1m29s[/video]