I wear a medium in Uniqlo oxfords and have a medium AD oxford from last season. The AD is slimmer and and shorter overall as you might expect. The best thing to do is measure a shirt you have and compare to the chart.
Well it looks like I'm part of the club. Just got home from work to find my washed apricot and peach ADs waiting for me. I got M in the white and L in the peach. Medium is definitely my size but the large works too. Looking forward to future purchases.