Yet another OR product that I find fantastic. It's light, packs tiny, actually breathes, has a great cut. I like that the sleeves are long enough and it works great for cycling due to extra length along the back. Stays comfortable even when putting out a big effort.
I'm 6'3"/180lb and wear a medium Revel. My chest measures about 39" and the OR size chart has medium at 40". It's a nice slim fit on me but I can still fit a thick fleece or similar underneath it.

This sack looks to be made well and is extremely easy to get sealed. The fabric portion looks very abrasion resistant, but I'm not sure how long the clear plastic portion will hold up over time (this is the part which gets rolled). So far so good though.

--Edit 08/22/2011
I have a small size WPF sack that I've been using for a while now and there is no longer any concern about the durability of the clear plastic, it's holding up great. I've changed the rating to five stars because they are a piece of gear that just works. I've since bought a couple more larger ones as well.

These boxers continue to impress - great materials, great fit, great performance. Wicking works well and the material never feels abrasive. Almost have my whole wardrobe switched out and threw everything else away.

It's been a while since I purchased my first pair of these and the original shows no signs of wearing out any time soon. I've gradually been buying more in order to replace my entire underwear supply.

Couldn't be more pleased with these boxers! Give them a try!

This is a fantastic deal if you get one of the colors that is roughly half price. Overall, it is well made. No problems with zippers or seams coming apart. It does a good job of remaining comfortable while fully loaded (tools + water). Some straps on the outside for attaching a rolled-up coat etc. would be nice, otherwise it's not lacking on features.

Simply put: Everything else now seems shockingly terrible in comparison to these. Give a pair a try, you'll never want to go back.

--As others have mentioned, sizing down is a good idea.

These appear very well made and are very comfortable with the use of different material thicknesses. As other have mentioned, the price can't be beat. I'll be buying more of these for sure.

One note: I've been used to thinking of cycling socks as "lightweight" all summer so I found these to be thicker than I would have expected for "midweight", but that's not a negative.