I had a hard time choosing flip flops because they all had so many negative reviews.  I'm happy with my selection, though.  I wear a size 10 medium or wide and I can often fit a 9 1/2 wide shoe.  The 10 medium fits my wide foot snugly but solidly.  I wouldn't recommend getting a size larger and definitely not a size smaller.

It's actually somewhat of a struggle to get them on after I get out of the shower and my feet are moist.  When my feet are dry, they go on pretty easy.  I don't wear them for any length of time but the first couple of days I wore them all day around the house without any pain or scraping off skin between my toes as someone experienced.

I didn't need any break-in period.  They are not soft to walk on but they aren't hard either.  I'm very satisfied.