I don't really remember it as hard personally, but I remember a lot of people saying it was and I suspect I did at the time too, it did get me to switch over from using pens to mechanical pencils for doing equations, which was pretty significant because it meant I could no longer work most problems without going back and making multiple corrections, it's also the first class where I started actually going to the prof's offices hours for help on a regular basis, because I remember we'd joke about how his office was a black hole you could never escape from if you went in for a question, on the other hand after that I generally found spending a couple hours or more a week in various prof's offices getting help to be totally routine, so it must have been fairly hard to have effected my study habits that significantly. There's also that 'we' aspect, I'd never need to study or do HW with anyone else before, after that I generally had classes composed of many of the same people who I regularly studied with, who for the first time were actually helping me as opposed to slowing me down. I generally tell people that Calculus is the boot camp for scientists and engineers but I think it's probably Calc II specifically for most of us. Not sure if that helps but what I'd stress, speaking as a physicist who studied with a lot of engineers too, is that generally it is the class where people often going in absurdly smart and thus a bit lazy, and come out adapted to spending hours a week on the homework from one class as opposed to five minutes.