For those who haven't used it, Goodhertz Canopener is intended to provide a similar soundstage and presentation of speakers on headphones. The idea is to tune the plugin's parameters until your headphones present similarly to your speakers in your room. That gives you a "trustworthy" way to mix on headphones when you can't or don't want to mix on your speakers. I spend a few hours over a few days tuning Canopener so that the mixes I was working on felt very similar when switching between speakers and my 'phones. I find it very helpful to hear a better sense of L/R panning and I can better perceive the volume of center-panned instruments when mixing on headphones. As Svyet mentioned, it's good to bypass is now and then for a "real-world" headphone check, but I'm never surprised when I bypass the plugin. It just helps me get a mix settled easier.