I generally like writing hooks. They're fairly straightforward to understand (until they aren't, but that hasn't bitten me often yet). However, reading other people's hooks is a lot more mental overhead than the same class methods, IMO. Either you have strict coding standards around them (which are pretty hard to implement with automated tools, so hopefully your code review process never lets anythign slip through) or comprehending someone else's code takes longer. For that reason, I've stuck with classes for the time being.