I dislike the speed of the web app, the lack of, that is. Also, sometimes it's not very intuitive and you could see it needs a lot of polishing. There are two UIs to the web app and the other is located once you click the "Competitor SEO" submenu in the "Tools" menu and this makes it very confusing (shuffling between the 2 interfaces).
I would advise people to stay away from the tool, at least while they improve their index and polish the app.
Also, the integration with Google Analytics doesn't go as smooth as you'd like. There's an issue when adding a new project. It goes through 3 stages (General, Keywords, Search Engines). If you don't add kywords right away, there's no "Next" button on the "Keywords" section and you can't move forward.
After using it a while, it does seem like a useful tool, just not very intuitive. It has steep learning curve, but it does provide you with some useful data.
The reporting part is done top-notch, but I dislike it doesn't suggest which keywords you should track like, for example, Ahrefs.com does. Overall I'd say it's not a premium SEO product, but it also does not cost premium.
Update: 1. It does seem to add the website when you don't provide a keyword list for it, even though it doesn't say clearly that it's added.
2. I've sorted the Google Analytics issue; my mistake.