Yay :-D I just finished my "Grumpy Chic Mittens" with some modifications -- I made it a convertible fingerless mitten.
I had to to do some unraveling and I am a loose knitter some my gauge is not the best (I have wonky shaping when there were switch three colors on round 13 and 33 of the chart).
I used the LB Basic Stitch yarn, but I made it mine using the colors of rich blue, spice orange, and charcoal grey (with some leftover scrap white yarn) instead of the taupe, ecru, and black.
I followed most of the pattern and chart.
For the thumb gusset, my thumb gusset was on round 6 to 18 (or 20) on the chart. For the increases, instead of the m1 (make 1) I used kfb (knit front back) because when I did the m1 I found my gusset I made was lace-like gap or hole.
Next, I finished off with kitchener stitch instead of the simple loop pull.
Lastly, I am finding those those giving unfavorable review are unfair and are most likely beginner knitter who not knitted mittens and made any thumb gussets. Therefore, although the pattern skill level is categorically "easy," the techniques of color changing, increasing for the thumb gusset, and picking stitches to make the thumb with are probably a skill level of "intermediate."
I will post photos of my finished mittens are on my Instagram.