its all I ever used, and knew existed until I came online and really look it up.
I got the smaller one and used it for 5 years, it works great. you can put about 30 grams of finely chopped up bud in the small one and 2 or cans of butane and I can get 7 g of oil.
I recently bought the bigger one which I dont really like that much. almost too big for me, and the back pressure it built up was crazy. I put 100 grams and 10 cans (too much butane) and got 20 grams of oil outta that one.
so yeah, I would say they work pretty damn good.
now how they compare to a long skinny glass/SS one is a different story.