The sizing, for one. I have a size 9 foot, which fit the "large" catagory on the pattern.
Also - the pattern was rediculously clear in some aspects (like showing photos of the slipper pieces before felting) but then very unclear on other key aspects - like how to assemble the damn pieces into the actual slipper.
But - I do still like how they came out in the end. I used PCW (Patons Classic Wool) for them. I put some fabric paint on the bottom for a bit of traction, since I was sliding all over our floors with these!
In other news - DH and I made home-made onion rings (home-made starting from buying the onions at the store - no we don't grow our own produce... yet...) and they were out of this world fantastic. You must try them, assuming you have a French Oven pot and candy thermometer on hand. And a quart of vegetable oil.