What does WordPress.org do well? What I love best about Wordpress is the learning curve is not steep and once you get the hang of things, you can really create an interactive and beautiful website. What it does well is allow the use of numerous plugins, most of which are free. The software itself is free to use and advanced coding knowledge is never required.
What does WordPress.org not do well? The load times can be very slow at times. Unless you are paying for a supercharged hosting package, prepare for your site to load a little slower than normal. I think that in the future, wordpress could optimize their code to make various sites run quicker. I recommend a lightweight theme when using Wordpress.
What do you wish you had known about WordPress.org before using? I cannot stress this enough. Wordpress is free, so you already save money from the start. Because of this, please invest in a really good wordpress template. There are professionally designed themes that will do most the work for you if you can't code. There are even some amazing free themes out there if you search. Installing is easy. I also highly recommend that WooCommerce be your first plugin you install. It is free and allows you to setup an online store in seconds. I sold a product my very first day. Wordpress makes all this possible and they don't charge for it which is unheard of.
Have you used a competitor to WordPress.org? If so, how does it compare? I have not used a competitor.