Personally, I haven't. But EGTs monitoring will allow you to see if one cylinder is leaner or richer than the others. The usually wideband setup just tells your the AFRs of all the cylinders combined. In a high performance/racing application it is a good thing to have.
I noticed the inlet of the DF exhaust turning white when it used to be painted black and started wondering if the EGTs are too high but they are the highest at stoic and I guess it just means it's no longer running too rich.
AFR is going to directly effect your EGTs as you know. The leaner the cylinder mixture the higher your EGTs will be, continues going up if you go even more lean than stoichiometric. One of the major functions of the fuel beyond creating the combustion event is keeping cylinder temperatures down. This is also key in preventing knock or detonation, which is why AFR is so important. EGT monitoring would just be icing on the cake in my opinion.
I've never had EGTs on anything personally, I know they definitely have their place but I feel like it's for those trying to gain that last 1 or 2% or just absurdly high hp cars where everything becomes even more critical.
I have a pyro on my diesel truck, but that’s so I can keep an eye on egt’s when I’m towing. I used to worry about getting near 1500* for an extended amount of time, but with some exhaust and tuning changes, I never get over 1280* anymore.