I've been using Klasse for almost a year now. I learned about it here. I started out using only AIO. It's a great product. It makes the paint feel buttery smooth, and it has a nice shine. Left on it's own, though, it seemed to me to lose the smoothness and shine in about 4 weeks or less. Perhaps the protection was still there, who knows? I'm not a good judge of how well paint is being protected.
I held off on using SG for a long time because of all the talk about it being fussy stuff to use. Instead, I decided to fortifiy the AIO with Sonus Acrylic Spritz. As far as I am concerned, this worked very well. A weekly or sometimes twice weekly application kept the shine and slickness going seemingly forever. Maybe not up to multiple SG coat standards, but it looked good to me. Once, about 2 months into that regimen, I took the car to the Pasadena Car Wash, where they have the option of getting a hand wash as opposed to the machine wash. I could see the guy who was drying my car call some of the other workers over to touch the paint. When I was called over to take the car, the guy told me the car had been really easy to wash and dry because the paint was so slick.
At the end of 4 months, the shine was still going strong, but my unopened bottle of SG was starting to call out to me. About that time I was reading about the Bill North WOWO method, and decided to give it a try. But - I'm lazy. My initial attempt was just the hood with a small Surbuf pad from CMA. I did not see any great improvement in the shine (but my car is white). Nevertheless, I decided to get one of their giant size Surbuf pads to do the whole car. I'll tell you, laying down SG with that thing was a breeze - about six quick swipes and the hood is done, then just wipe off. Just try to miss a spot with a pad that huge!
My latest deal, again because I'm lazy, has been to resurrect a method written about on this board quite some time ago. I got a small 8 oz spray bottle. I put in 7.5 oz of distilled water, and 1/2 oz of SG. After washing the car, I shake the mixture well and go over it with this stuff instead of Sonus. It took only 4 oz of this mixture to do my Accord - that's only 1/4 oz of SG consumed. And that included the wheels. Cheaper than Sonus, and maybe the concentration of SG in my mixture is higher than Sonus. I am very pleased with the results, both in shine and the tactile slickness.
Bottom line: I don't think AIO alone is enough. But using a spray like Sonus or water plus SG after every wash seems like a very easy and painless way to get and keep the full Klasse shine and slickness.