I just received a top and bottom today. Thanks for the heads up!
Good stuff and worth the price. However, this merino wool is itchier than Icebreaker (the only other merino wool I have to compare it to). To me, the Icebreaker 150 shirt I have feels like the most comfortable thing I've worn besides silk. The I/O top feels like it has more of that regular wool itch to it. I'd definitely buy the bottoms again because my legs aren't as sensitive, but I'd save my money for the expensive, yet super comfortable Icebreaker tops.
As far as sizing goes, I'm 5'10", 32 inch waist, 155 lbs and pretty skinny overall. The small bottoms fit me perfectly (form fitting, no saggy butt, extend to an inch or so just above my ankles), and the medium size top is probably also the right fit, although a small might have been ok because the sleeves have a little bit of extra length in them and the material stretches easily in every direction (enough to add thumb holes or loops).