Most versatile underwear ever!
I use these boxers daily for everything: trail running, rowing, under waders while fly fishing, for daily wear around town and at work, for bike commuting, etc. The fabric is a heavier weight than other brands of merino boxers I've tried and also softer and higher quality. Quite nice to wear even on warmer days into the 80's - 90's as the fabric miraculously manages moisture and doesn't ever get heavy, sopping wet and clammy like cotton or stinky like synthetics after a long day of aerobic activity. How nice is it to drop by a local cafe for a bagel and coffee or pick up the kids at school right after a hard workout and no longer have to be concerned about the cloud of polypropylene-induced stench surrounding you? I'm 5'9 and 165lbs and the medium is snug enough fit to provide sufficient support for active sports like trail running, soccer or cycling. Waistband is comfy and the slightly longer legs of the Zepher have totally eliminated the rash on my inner thighs I used to get from my running shorts when wearing a traditional athletic supporter for longer distances. I bought my first pair of wool boxers about about a year ago after experiencing the wide comfort range and versatility of Ibex wool shirts and tights for rowing year round in the Pacific Northwest and have never looked back. I recommend retiring everything else in your underwear drawer and getting at least 2 or 3 pairs of these and 2 or 3 pairs of the lighter weight Ibex woolies boxers. They're really that good a product. Buy just one and I promise you'll be hanging out next to the dryer waiting for it ;-)

Nice and warm
I wore these on a 2 day backpacking trip in the Smokies. The temps dipping down into the low 20s and my bits were never cold. They did a nice job keeping me warm even when I was hanging out at the campsite. I'mnot sure about the durability but Ibex typically makes good products.

Great product
I highly recommend these boxers - they are great and adjust well in warm and cool environments. As you probably know they have all the advantages of wool so sweat wicking, fight odor, and dry quickly. Ibex in particular are impressive because their stuff (or these boxers anyway) are made in the USA unlike Icebreaker which are manufactured in China (though both use New Zealand merino wool). The important thing to bear in mind with these boxers is that they naturally sit quite high on the body - maybe half an inch below the belly button. For outdoor activity, etc. this is good as helps ensure no part of you is exposed but for casual wear it is a little less helpful. The boxers can sit around normal boxer height (i.e. closer to 2 inches below belly button) but then they bunch slightly. From my experience its no problem really but if you are looking purely for casual use wool boxers I'd maybe try for a pair that sit a little lower on the waist. If you are debating the value-for-money of these just consider that if they last 200 days of wear its only about 25 cents a wear. And I would be surprised if they don't last longer than that! I'm 5'10" and 165 lbs and a medium fit very nicely.

Perfect baselayer
I picked up these for backpacking, and will be getting a couple more pairs. The thickness is great, very soft, and the elastic waist is also very soft. Unbelievably nice underwear and would wear everyday if I could afford to. Merino is easy to wash and dry on the trail, and keeps you warm if conditions get cold and wet. These are the perfect weight for me, I don't see these being too hot for me at all.

Super Warm, Very Soft
They keep you very warm, and are soft to the skin. Haven't tried them in the summer yet, they may be too hot, time will tell. Another bonus is that you can get a few uses out of them before they start to stink. Also very durable. I had a pair of icebreaker merinos tear on me, but these ibex are rock solid.