I think he's great. He backs up his research with lots of good primary and archival sources and he is one of the few voices pushing back against the anti-communist historiography that has sadly become accepted as the norm. Obviously he has a bias, but then again so do all historians whether they admit it or not. None of his detractors are able to actually prove him wrong with any solid evidence. They end up resorting to circular sourcing from other anti-communist propagandists and anti-Stalin myths that have simply over the decades become axiomatically accepted in western academia despite dubious or nonexistent evidence and if you dare question them you are accused of being a "Stalinist". Even after the opening of the Soviet archives in the 1990s to researchers ending up outright debunking many of these narratives a lot of western so-called historians continue to peddle the same nonsense.
Imo i think all communists should at least hear what Furr has to say and not automatically dismiss him without even looking at the evidence and arguments he presents and just writing him off because his conclusions don't align with the biases and "commonly accepted truths" that we have been taught by our deeply anti-communist educational system.