The pattern prints out well and the instructions are easy to follow. My only complaint was that the largest size is missing some of the marking dots on the pattern. I emailed the designer to let her know, but you can definitely wing it by looking at the other sizes, too. And since I don't have a baby myself, I have no idea how the sizing runs.
This pair is the 0-3 month, for a little baby boy. I haven't heard back from his mom as to how they fit.
This pair is the 3-6 month, for a little girl. Her mom said that the feet fit fine, but the ankle area is too big. But she also said that the elastic length was fine, so I'm not sure what needs to be fixed there.
And this is the 6-12 month pair, for my niece. They were part of her birthday present, but apparently they were too big for her. (And I'm not sure how she ranks on average size.) Granted, that was two months ago, so maybe they fit by now. :) If not, I might make her the smaller size.
The boots turn out awfully cute, and they are easy to make and use up some scraps. So the sizing issue is my only real quibble. I've asked my sister-in-law for a tracing of my niece's foot, so maybe I'll be able to tell better once I have that to compare to the pattern. Oh, and since she's now walking, I would add gripper fabric to the bottom of the boots.