Existing users, 
Just tried KNO and the main difference is that DG does the "move the tiny dock location" thing so well. This matters if you have hotcorners. With KOD the presence of its minimized Dock conflicts with that corner (is also 3x longer than DG's - at least on my system). With DG when you mouse to the corner where the Dock might popup the Dock shifts to the opposite corner making the previous corner easily available for hotability.
Still, for the difference between free and $10 ($15 once out of beta), each user must make a decision. Me, I'm opting for DG.
Dock Gone
Keeps the Dock out of your way.
Version: 1.0.2
more on KnockOutDock v. DockGone
Feedback Type: Commentary
Contributed by: tim.lance Tuesday, May 05 2009 @ 06:05 AM PDT
Product Platform: MacOSX
Used Product For: Less than a month
Recommend Product: YES
Comments
more on KnockOutDock v. DockGone - tim.lance
Interfere was the wrong word as functionality does remain. But going down to the corner brings up KOD's Dock. Not very elegant. Cheap; yes. The latest DG may be perfect. Heck, I paid up when the developer had the little thing go to opposite corner of where the mouse pointer went. Now I'm even happier. I've been working all morning, using a total of 9 DragThing Docks covering all 4 sides of my screen and have yet to see anything popup anywhere (using latest v1.0b3.1).Wednesday, May 06 2009 @ 08:29 AM PDT
more on KnockOutDock v. DockGone - artie505
I don't know what configuration you're running, but KnockOutDock's dock does NOT interfere with any hot corner option in SysPrefs or the Butler pref on my deuced Mac(hina).Reply to This
Wednesday, May 06 2009 @ 06:04 AM PDT