I think the quad curve EQ is really great and I frequently find its results preferable to others I try on the same part. I also like its ease of use. So total thumbs up!
I've continued to get better at mixing, and one technique I've picked up from someone in some explanation is the idea (if appropriate) to EQ a part before passing it through a compressor. Just an example of that would be to EQ a guitar track coming out of an amp sim before putting the track through a compressor. This allows to EQ out some of the high scratchy stuff and/or low end which can help in what results from the compressor.
The point being I see the usefulness of using more than one EQ on a track as appropriate. One sort of as a pre processing EQ and the other, presumably the Quad Curve EQ, finishing it off after the processing to get the right tone overall.
I put the extra EQ in a ProChannel FX chain module to allow positioning within the ProChannel flow.