I recently purchased a Merino 125 T and a Merino 145 Zip-T from them. I've been very happy with both pieces. If you shop around, you'll see that their base layer prices are very competitive.
I also purchased a pair of Attack Pants used and have worn them on a number of hunts this season. I really like these pants. The 4-way stretch material is very comfortable and the overall design is great (the cut, functionality of the pockets [cargo pockets that are actually worth using], etc).
My only (minor) complaint about Kuiu is that it can frequently be difficult to find certain items in their camo patterns (at least at/near the fall hunting season), especially the popular Verde pattern. However, they offer a good selection of (muted) solid colors that are actually useful for hunting (I really like their Brindle and Forest colors).