I’m currently trying Duckworth, I’ve been liking them. They’re a bit of a novelty in that the entire shirt is made sheep to shirt in the US. Only a couple of their lines are pure wool, though, so read carefully. The fabric seems a bit heavier/less soft than others, but they’ve been holding up better so far. Maybe related?

Icebreaker seems like the biggest brand in merino, and their shirts are pretty good, very light and breathable, but a bit fragile (my jeans buttons seem to be forming holes in them somehow, all in the same spot). Big fan of their long underwear, too, makes a huge difference in the winter.

Woolly shirts are super soft, probably the most comfortable, and not too expensive, but even more fragile than icebreaker IME.

Still looking for the perfect shirt, but I’ve liked the ones I’ve had from all of these.