These are pretty good.  They're definitely better than Fruit of the Loom brand boxer-briefs.  There's a little bit more pouch in the front of these, which helps support everything while moving around.

They breathe well and feel well ventilated and cool, even at the end of the day.

Unfortunately, the elastic/lycra/spandex/whatever content is low enough that these will stretch out throughout the day.  Support and fit decrease, and waistband rolls up by the end of the day.

Overall, I rate these 4 of 5 stars.

X-Bionic brand hold their shape better throughout the day, but don't cool as well as these.