I am a 10 1/2 Wide (11 W is what I usually have to buy).  I read the reviews and took my chances, even though I couldn't go up a size like people recommended.
I bought an 11, and the actual footbed fit with plenty of room, but the instep is not high enough, especially towards the ankle.  I have extremely wide feet, so I can't imagine this boot not being wide enough for anyone's foot.  But, unless you have a low instep--in other words if your foot is the same height from the toes to your ankle, it will probably be too tight for you.