I bought one and use it on a customer's cars who wants me to use a hose but doesn't have a water deionizer like his partner does.
The initial rinsing pressure is decent. Not quite as forceful as some nozzles, but more than enough to spray the vehicle down pretty good. The soap seems to work well, no problems getting even his normally nasty Excursion clean. The switching back and forth can be awkward at times but after a little practice, it becomes pretty easy. It is a bit disconcerting at first when the beading goes away when rinsing off the soap, but that is intentional and it will bead again the next time it gets wet.
I agree the filtered rinsing stage doesn't use a lot of water pressure, but part of the problem is the filter's base needs to be pushed towards the back of the unit or it doesn't seal properly and water leaks out of the bottom. If you position the filter right, no leak and noticably more water pressure. It still does take some time to completely displace the non-filtered water though.
Does it dry spot free? Well, spot free air drying isn't my goal with the product. I use it because my customer doesn't have a completely shade free spot to wash the cars in, plus they are all black. It is nearly impossible to wash them and get 'em back in his garage in the summer and use my vac to blow water out of the body seams without water beginning to dry on the paint, so I used the Mr Clean system to buy me some time. I've noticed since a lot of water sheets off, drying times are reduced and no more hard water spots on areas I can't dry quickly enough.
If you use the Mr. Clean system and leave your vehicle out in the open to air dry, you will get spots, mainly because any dust or pollen in the air will settle on the wet paint. If you have a blower or a vacuum that converts to one, you can probably use that to dry the car pretty quickly.
I did use the Mr. Clean system on a Chevy Silverado 2500 last weekend and allow it to air dry, and you could see on the hood where some dust had settled before it dried completely and some QD took care of that. Otherwise, I didn't see any noticable water spotting.