I already had one of these on another rifle, and I have been very pleased with it. I have never needed to re-tighten the unit and it is rock solid.
I have never tried a swiveling unit, but I don't know why you would want that when you can just adjust one of the legs a little longer. I can understand the model with the leg notches, as that would give you definite adjustments if you are doing benchrest shooting and need to know that your horizontal crosshair is even with the horizon, but I prefer the infinitely adjustable legs on this model.
You won't go wrong with a harris. The only hard part is mounting to a picatinny, which I would recommend either 1) Badger Ordnance TRAMP or 2) Harris Rota-Pod. Either way, this bipod won't let you down.
Pros: Solid, Robust
This review was written in the old system and had content requirements that are different than reviews written today.