SP, once again, there are rollers on the ropes which prevent it from seesawing. Have you actually seen one in use in real life, rather than just reading or looking at drawings?
Because I have seen a Pessoa system used a number of times, and I can tell you from an eyewitness view, that the system ABSOLUTELY DOES NOT 'yank and pull the horses everywhere making it more confused'. The horses that I have seen travelling in a Pessoa system, have gone very sweetly and happily, there was no see sawing action to be seen, the horse can easily raise it's head but the system merely encourages the horse to stretch over the back.
It is a far more user friendly system than side reins, which are a great lunging tool if used in knowledgable hands, as the bum rope is encouraging the horse to engage its hind legs rather than needing the lunger to concentrate soley on the hind legs when in side reins to prevent the horse leaning and falling onto the forehand. The Pessoa also prevents the horse being able to lean against a solid contact, but still gives a constant contact so that it is not being hit in the mouth at every stride.
If the rollers were not on the system, then YES it would be see sawing, but because the rollers are there, as I explained in my previous post, they take the motion of the hind legs moving and allow the contact to the bit to remain steady.
No I do not use the system, I don't feel the need to but I can definitely see its benefit.
As for you comment 'get on the horse and ride it' fair enough if you are a knowledgable enough rider to ask the horse to come together without interfering with it's balance or pulling on the reins/giving inappropriately timed releases, but for many people this is not the case and they need a helping hand. Lunging systems allow the lunger/rider train the horse without the added weight an imbalance of a rider as well. This also encourages a horse to pick up it's back far more readily than it would with a rider on board when it is still only just developing the necessary strength to lift it's back.
You use draw reins on your horse - would you like me to fight tooth and nail about how horrendous the results of draw reins can be? Everything has it's place. Draw reins are certainly not user friendly. I have used them only a handful of times a a very select few horses who travelled inverted and were genuinely confused as to whether they could actually lower the neck. Namely ottbs. Overuse leads to overbending, sucking behind the bridle to evade contact among other issues... so I'd be careful about yelling good and loud about how terrible a Pessoa system is ;)