Haven't used them, don't know anyone who has.

The testimonials on their website indicate folks are happy.

However, the testimonials indicate the same type of results I get with the kingpin tripod I use. Once I put the weight on the tripod the rig becomes rock solid, no side to side or forward to backward rocking.

Looks like the Winfield would be easier to setup since they mount to the landing jacks. I just don't know if it they would provide the same level of solid the tripod offers. I can actually raise the landing gear off of the ground while the tripod is in place (I built it out of steel tubing). This allows me to place extra boards if I'm having trouble getting the 5er level.

Also has come in handy once when one of the landing gear quit working and I had to take it a part, also when I had to raise the 5er up higher than the landing gear would go to solve a hitch problem.