What does Squarespace do well? I used Squarespace for my catering business's website for over 2 years and have always been impressed with the platform. It's incredibly intuitive - it's the easiest website creation software you could imagine. You can basically just drag and drop elements anywhere and they'll be updated live on your website. It's the easiest platform I've tried for website design. Their designs are beautiful and functional- they make it easy to customize your page by uploading/ swapping imagery, changing formats, fonts and getting your site up and running with almost no down time.
What does Squarespace not do well? Nothing major, honestly. When building a page there isn't a way to see how it will appear on mobile, so it takes a little back and forth to get that right when they could have a mobile preview feature or something. I believe that Squarespace's SEO capabilities are somewhat limited and could improve upon. Other than that, I have not found anything that I dislike.
What do you wish you had known about Squarespace before using? Many of the default templates that the platform has, I consider them very old and aesthetically are not well designed.