What do you like best?
As a web developer, I can say that this is a wonderful tool to reduce the time required to build an HTML+CSS website, since you can build everything visually, without (sometimes) even looking at the code.
Also, the Wordpress integration is very great, helping a developer create templates very fast.
It also comes with an option called "Bootstrap Blocks", that are pre-loaded pieces of code that save you a lot of time, specially when it comes to mockups (for production sites you might prefer to code your own styles).
They have video tutorials available that can help you get used to the program.
What do you dislike?
Some might say that the price is not too high, but considering the benefits, I would highly recommend it.
Even when the interface might seem familiar, it takes some time to get used to all the options available.
Recommendations to others considering the product
Even when it is a WYSIWYG tool, it is highly recommended to know a great deal of HTML and CSS before using it, since you need to understand the different options that you will be using.
Also, remember to watch the video tutorials available. They will save you a lot of time while learning the tool.
What business problems are you solving with the product? What benefits have you realized?
The main benefit I've found using Pinegrow, is that I can reduce development time considerably, specially when it comes to build a Wordpress template (assuming you've paid for that option).