is using ahrefs for free still worth the effort?

Connect it through Search Console when you set up Webmaster Tools - it imports your sites in a couple of clicks instead of messing with verification files. For occasional competitor checks, Semrush's free account gives you a handful of lookups a day, so mixing the two free tiers gets you further than either one.

For your own site, yes. Ahrefs Webmaster Tools is free once you verify the site and gives you the site audit and your backlink list, which covers most of what a small site needs. The free checkers on their website (backlinks, keyword ideas) are heavily capped and only show you a slice of the data, so for spying on competitors they are more of a teaser than a tool. If competitor research is the main thing you want, you will hit the wall fast.