I find that I get itchy in Merino wool underwear so thought I would try the Alpaca boxer briefs as an alternative. Very soft and a good fit, without the itch. I wore them on a 4 day hike in Tasmania and found them comfortable and they didn't get too much stink. After the hike they had a 1cm hole in the crotch and the elastic had pulled apart a bit at a seam. I have worn them probably no more than 5 times since the hike and they are wearing though in the seat area and holes are appearing in any area where there is any friction.
The boxer briefs are a nice product but they need to be thicker and to be blended with something like Tencel or cotton to have enough strength to handle any activity such as hiking. At AUD$82 (inc. $18 freight to Aust.) they are not good value if they wear out so fast.

Soft, excellent light layer but a bit tight around legs & crotch due to design. I'd prefer and would buy boxer style underwear.

I get quite an itch from good 'ol sheep's wool, not so much with Merino, and none at all with these alpaca underwear.
They fit great (usual underwear size), and eerily don't smell after several days use.
100% satisfied thus far with my 100% alpaca wool underwear.
Be aware, there are other places that sell alpaca wool apparel, but this is the one place that I found that sells 100% alpaca wool.

I purchased two pairs of these briefs to wear on alternating days while hiking the Pacific Crest Trail and was excited for their softness and the natural fiber's ability to reduce odor. However, within 60 total miles, both pairs were completely useless.

The fabric rubbing between my legs eroded away almost immediately; I noticed the holes at Mile 30, so likely they didn't even last that long. By mile 60, both were completely useless.

Nothing on the company's website suggested the briefs would be ill suited for backpacking; in fact, in multiple places, Arms of Andes promotes the briefs as "The Perfect Underwear for Hiking", saying also that they are "designed for backpacking". Clearly not.

For further insult, Arms of Andes has determined that my case is not eligible for refund or other compensation. I'm not sure what conditions would have to exist for them to consider a product failure their own fault, but this seemed a cut-and-dry incident to me.

So now, I'm out $80 within a matter of days and have no refund with which to purchase replacement briefs. It's frustrating the product was so poorly suited for backpacking, but it's insulting that the company won't stand behind their product. Their customer service has been receptive to feedback but has stonewalled any requests for reimbursement.

I like the feel and sizing but the part by the bottom middle seam (lower crotch) has worn away and holes have appeared after about 10 wears. Other pairs are holding up with the same use.