This is - hands down - the BEST SEO software on the planet. The only thing it does not have is a decent on-page grader, which they are already working on and once it goes live, it will be the ONLY tool you really need.
I currently use MOZ for on-page grading and I use SEMRUSH for backlink assessments.
ahrefs dot com deploys a content scraping bot to gather data about competition websites for their service. This bot is very rogue and poorly constructed. It often ignores robots.txt rules and scrapes websites at speeds sometimes exceeding tens of thousands of pages per day.
I do not trust this website. Do not support them by purchasing their services. And if you host a website, be sure to block the bot using the following in .htaccess:
SetEnvIfNoCase User-Agent "AhrefsBot" badbots
(and then after your Order parameter for access control, add:)
Deny from env=badbots