I'm going to be honest, what I really don't like in mods is an attempt in realism that isn't really work. For example, the pressure chamber from pnuematicraft seems realistic, but due to the fact that air of the same pressure is within anything it is compressing, in real life it would have basically no effect. I prefer mods to either be very realistic, or say, "This is a video game, not real life, so I'm doing it my way," as apposed to things like pnuematicraft or many other mods that seem and act realistic but really aren't, and can lead to misinformation.