A little expensive. Support responses can be slow. Interface can be rather confusing although they recently improved it a lot (see above re: regular updates). I couldn't get the Chrome Extension to work in any of my installations of Chrome, so I still use competitor toolbars in my browser. You can't ever change your login email address thanks to the billing system, so choose carefully.
Basically, Google shows the autocomplete suggestions whenever you start typing anything into Google search box. It is in Google's best interest to show the most relevant keywords in the autocomplete suggestions. Keywords that would help Google to retrieve the most relevant websites and help users find the most relevant content for their search query. 

Ahrefs also helps users dig deep into their competitors’ search traffic with the Positions Explorer tool. You can easily see the keywords the competition is ranking for in the search engines as well as the keywords they are spending on for their advertising and marketing campaigns. Even better, you can see the flow of organic and paid traffic they are receiving.
What would be the purpose of/reason for moving back to a different url? If its been a few years, I’d leave it alone unless you watched everything decline since moving to the main url. Moving the forum to a new url now would probably be a bit chaotic, not only for your main url but for the forum itself…. Only reason I could imagine myself moving the forum in this scenario would be if all those links were really awful and unrelated to the url it currently sits on…