If we were comparing SOG Folders with those of Kershaw, Spyderco, and Benchmade, I'd place SOG on a tier just beneath the other three.
SOG fixed blades are between good and really good, even the ones from Taiwan, but their folders in my experience are pretty generally sub-par, regularly suffering from problems related to F&F and QC.
Still, most will make adequate cutting tools, or easily replacable beater knives. A few of them (Arcitech, Facet, Stingray, etc.) are sleek and elegant and worth owning, but not at the price SOG sells them for.
If there's a particular SOG folder that you like, I would go for it. At worst you'll learn a lesson.