I have used a bit of their stuff.
The merino Haven 4-ply: I found it a bit splitty, after tinking it just once or twice it would look nasty and ratty when unknitted, fortunately it knits up okay even then, but I prefer Patonyle instead, equally soft and wears a teeny bit better.
And the nicely dyed '4-ply' in hanks, gorgeous colours and we don't have any other handpainted/whatever available here, but it knit up so thin I would really call it a 3-ply, not quite right for socks as I had intended.
Oh and the Merino et Soie, not as nice as I expected, I wondered whether it was third-grade silk and 3rd-rate merino, a bit scratchy, however that was a dark colour and the lighter colour of it I used was much nicer, seems to be the way with many light colours, something about the dye I guess.
I do however intend to keep an eye out for other products by them when appropriate for a project and try out a bit. I think that the $3 a ball merino is not quite as nice and well-spun as say the Rowan but for 1/6th the price I don't mind. Which wools of theirs did you like?