I have no idea how or why the curves work. All I know is if I try to use em my audio pops off, or the whole project crashes. So, I just customarily leave it alone. Got an Ol dusty analog EQ to run through if I really need it. Little sliders I can understand, lol!!

I've read (and tried to understand) what each curve does, and have tried to put each into practice when searching for the "right" EQ on a particular sound.
I found it difficult at the beginning, but after much time, and listening, I am finally starting to hear the differences, and can even match what I'm looking at, to what I'm hearing some of the time.
I have never used a large format console in a "real" studio (I was never allowed to touch the dials). I don't have the ears to match what I'm hearing to any particular console, but I realise that is what those curves are trying to emulate.
Personally I've found this EQ to be almost everything I need, there are so many ways to alter the sound with this one EQ. I rarely use anything else unless I'm looking for a particular sound, or need an EQ "before and after", and need two or more EQ's on a particular sound.
Craig, any tutorial on how to use and setup a particular FX is going to be welcome and read by myself, and others I'm sure. The Quad Curve EQ has so many features it's surely welcome to be reminded of its many applications.

I'm not sure what is meant by the original question, but the way I use EQ is fairly simple, and is from a trick I saw used by a professional (although I imagine I don't use it as well as they do).
 
Using a graphical EQ, I play a track in solo, and sweep across the frequencies, boosting them.  And when I hear the frequency where it sounds worst, I cut that frequency by few DB.  Seems to help get good clarity.

I switch around depending on what I need, but usually the first mode is sufficient on instrument tracks. I don't use it for EQ on the master bus.

rodreb
YES! YES! To Pro Channel preset capability!!!!!

Just to be clear, the ProChannel does have preset capability. It's just that the individual modules within it don't.

BenMMusTech
The pure on mastering is a revelation!

Agreed, that's my favorite for general tone shaping.

rodreb
YES! YES! To Pro Channel preset capability!!!!!

+1

BenMMusTech
I worked it out but I still refer to the instruction manual every time just to make sure...
 

I think that link really does a good job of explain the differences (as long as one understands concepts of basic EQ and Qs)
 
LOVE the Zoom out Quad Curve in the pro-channel.  I'm beyond shocked to see posts of other people looking to other plugins to do the same task.  
 
The ability to create and save presets would be nice as I use the EQ on most channels and frequently deal with similar settings for certain sources.  
 

Anderton
..and use particular curves for particular applications? And if so, which curves do you use for which kinds of tracks? Inquiring minds want to know...

To answer your question  ........I have no idea!
 
I can say that I will place myself in the "Do Not Fully Understand" column.  So hopefully we convince you to write a column.  That would be very helpful.  Your Sonar articles are one of the first things I read each month in Sound on Sound magazine.

I don't stand in opposition to anyone's feature requests or anything, but honestly, EQ presets are the primary enemy of good mixing. There is basically never a good reason to use one.