It feels like it was made for me.  High hopes for this shoe.  I had read that the women's styles are a little narrower than the unisex which stands to reason and appears to be true.  I wear an 8 1/2 to 8  and the 39 medium was the perfect choice. Wearing in the house with socks to get ready for spring since it is 6 degrees here now.  Love the shade of purple.  You can tell it is purple but it doesn't scream purple.  I will be proud to wear this cute sandal anywhere!  I just got my first pair of Birkenstock yesterday(from Amazon, of course) and this pair today so I hope to be a convert! the ones I got yesterday are the Larisa sandals and these are way more fitted to my foot and liking.
***UPDATE****  I was WRONG about the size.  Go smaller and don't make my mistake.  I am now stuck with 3 pairs of Birkenstock in the wrong size because I didn't do enough homework.  But........  I love them and will try to get my daughter to wear them since they fit her larger foot.