From a mixing perspective, there is nothing worse than a bad sounding hi-hat in a mix. In some cases, they shout such annoying freq's similar to the annoyance of a baby screaming during a romanic moment, or, 60 cycle him, AC noise, standing wave etc. etc.. I'd rather have no hi-hat than one that is augmenting, exaggerating, contributing, accumulating sss and top end sibilance, including phase swirl to vocals and all other tracks in a mix. They will accumulate positive or negative attributes in everything so all I can say, spend good attention to detail when it comes to a busy track with hi-hats. One of the first things I do to improve a mix is to source out the hat-hat + bleed and listen for issues. The worst mixes I hear usually include phasy sibilant hat-hat bleed from poor micing, poor quality gear, bad conversion character and overdubs that have different versions of bleed. They are one of the worst offenders home studio recordings possess but when you get them right, they are equally as awesome for creating feel and life to any song. For pop and basic 4 on the floor rock, I'd replace them 9 out of 10 times with my drum replacement arsenal and never look back. Being said, if you want to help improve your mix... this is what I deal with all the time. For all other music genres, invest in the better gear that can handle their requirements to capture hi-hats accurately. Learn how to track them best you can because they are what I hear as a deal breaker for poor, good, better and best sounding mixes and vocals. They can be like a bad virus that accumulates. De-essing isn't really my thing but they can help sometimes. I will more often use object editing in Sequoia to cue out the worst freq. What do you do to the accumulating track bleed from room micing or headphone bleed as well? What about the clients that use autotune or shift various tracks in their editing or overdubbing process which includes even more pieced together hi-hat bleed or no bleed? Thus creating dynamic phase level swings that are now randomly shifting bar to bar. It can get worse.. the client is convinced hybrid analog is the next best thing. Not paying attention to how the voltages are randomly shifting the transients away from the original overhead bleed? Ah, the beauty, pros and cons of round trip processing. You not only have bad hi-hat bleed but now hi-hat bleed at a different pitches in a song. Same goes for cymbals and crashes. These fast transients and particular freq points demand stellar conversion counterparts and attention to detail. From a mixing perspective, how do you deal with hi-hat issues?