Benjamin P.wrote a review of Icebreaker Relay Boxer Brief - Men's on August 19, 2014
Familiarity: I've used it several times
Fit: Runs small
I wear them for everything, which for me means casual wear, biking (upright and recumbent), dancing, yoga, trail running, playing cello, catching a pint... I'm fairly slim: 188cm, 75kg, and wear a size large in these, which seems odd (31" waist pants (measured, not vanity) tend to fit me best). On me these do not ride up, but are in fact the second-best underwear I've tried.
The best was the Icebreaker 200-weight GT Sprint, now discontinued. So I guess it depends on your shape. My other 150-weight Icebreakers, the Anatomica, occasionally ride up, and don't fit me as well. But the bigger problem with those is that the fabric is thin and doesn't last very long. I worry that these will have the same durability problems, but that remains to be seen. For now they get a perfect score...