I've been using Foundry paints for a while now and I love'em. They are notorious for being very thick; like foundation paints before there were foundation paints. So not only do you get 20ml of paint, but it needs to be thinned with water or alcohol whenever you paint. So I would say that is the main con; it is not a good straight out of the bottle paint. And then there's the bottle, which I love and keeps the paint fresh. I have
GW paints from 1989 that confirm this. However, some people complain about the caps breaking. And while I have had 2 break over the years, they are easy to replace. Black Hat miniatures sells empty bottles and caps. So you cut the old cap off, and shove on a new one, re-pull the zip seal, and bam, brand new cap.
Here's the Black Hat link:
Black Hat Miniatures Empty Bottles
And I've attached some pictures of my Foundries in their triad order and some pictures I did of Vect in the Wargames Foundry paint style (which I also like).