I own a fairly large variety of their products for scale modeling: washes, oils, pigments, books, and some resin kits.
In my opinion they're probably the highest quality products on the market in their respective areas. But you pay for that too. Their stuff is FAR from cheap and, in many cases, isn't even something I'd consider reasonably-priced. I'm also partial to ProModeller products (now called Flory Models). Phil Flory's products are considerably different, with his washes focusing on pigment-laced solutions rather than oil-based washes and filters from Mig Jimenez, but they work very well. Both are very prolific scale modelers with different styles. Phily Flory recently added pigments to his line but I haven't tried them, but they're far more reasonably priced than Mig's offerings.