The pattern was easy to follow, only I was stumped when it came to the lace pattern on the sleeve and cowl. I ended up using a different lace pattern for the sleeves and just did garter stich for the cowl - worked out fine.
As for sizes, I went with the small size but made the sweater longer. The sleeves should have been even longer, they’re a little too short for my taste and I even went with the medium length (not small).