Shipping: the brand is based in London, so if you're international, you're paying a $20 shipping fee which is a third of the shoe price to begin with. If you are ordering from them, I'd make it a big order to make the shipping price make sense.
Sizing: true to size! I am a 7.5 but bought a 7 as they didn't have half sizes and it fit well. Super comfortable as well.
Quality: Putting on the specific sock boot I got was difficult and one of the rhinestones popped off in the process. I'm not too sure if it's just this shoe that is a little finnicky. I assume the regular heels are comfy and not difficult to put on!
Simmi has been my go to lately for shoes. The pricing isn't bad and the quality has been great. I like that they don't have that cheap feel to them. Take it from a girl that buys new shoes for every event so i don't have a fortune to spend. I would have given them 5 stars but the shipping is extremely slow. Takes about 2 weeks for a New York delivery. (Granted this is a UK site). I ordered 4 times with no issues, so I cannot speak on customer service or returns unfortunately.