I love merino wool. In fact, I prefer it to cashmere. I would say it is *almost* as itch-free as Smartwool.... but not quite. I do wear my merino cardis with a layer underneath. I can go with a sleeveless blouse and not itch on my arms. I also have a couple of v-neck merinos that I have worn with no layer underneath.
I have sensitive skin but here's the thing I have learned about wool: you need to wear it a few times and then it stops itching!! It's not that your skin gets de-sensitized; it's that the oil from your body rubs off on the wool. But, once you wash or dry-clean the wool, you have to start all over again.
As for the merino, I vote to give it a try!! Get a cardigan to start - that way if you find it too itchy, you can wear a layer underneath. I really like the BR V-neck merino cardis. (which I think I mentioned already!). I am finding I wear them constantly, they are so toasty warm - mind you, I do layer: with a knit or blouse, and also a cami if it's cold enough. So three layers. But, these merino cardis are lightweight enough you don't end up all bulky, which is one reason I love them. You get warmth without the bulk.
Smartwool is still warmer though...
