I have the system, I currently use it on my Nikon stuff so I have the 52mm adapter that lets me use it on most of my standard Nikon lenses (28mm, 50mm, 35mm etc.). But lets discuss the system a bit,
Its not exactly "high quality" so dont expect something that will stand the test of time. That being said, I dont use mine all that much (its mostly a holder for the graduated ND I have for it) and its faired really well. I have had it for 3 years now and no issues thus far. It still holds the filters quite well and does what it needs to.
The filters are good (not great) but I cant say its that limiting for my hobby work. I really have it for the Grad ND as thats one of the last filters you actually need if you want to capture everything in one exposure. Most other things can be corrected in post (assuming you are talking digital here).
I have not had any serious problems with it and would happily recommend it, as you note its a better price than the competition. I will admit there is some cool stuff out there when it comes to holders that can hold and rotate polarized filters which is neat but at the price bracket the cokin sits thats just out of the question.