It seems (by the look and by posts on other forums) that the GFS pedals are re-branded BiYang (sold mostly on eBay) pedals. The price/feature point on them is very attractive. I have been tempted on several occations to buy one (BiYang) from a seller on eBay, but never did. The one that caught my eye the most was one that had a user-replaceable op amp chip (thru a hatch on the bottom), and even came with several different ones, including a 4558 "Tube Screamer" chip. Let us know if you take the plunge on one of them.

By the way, my pedal collection includes some Behringer stompers, which also have a very nice price/feature point.