I wouldn't say that it's "not hard", but I also don't think it's that hard. Before playing it I was expecting this brutally difficult and unfair challenge that would be all but impossible to overcome, because that's basically how people describe it. But I quickly found that it's really not. Yes, the game does punish you swiftly and without mercy if you're being careless, and yes, you'll probably die a few times on each boss before figuring out the weaknesses in their patterns, but once you understand what to do it's really just a matter of careful execution. I don't think any boss has taken me more than 5 tries or so. O&S I believe I beat on my second or third try (although that was with the help of dear Solaire).