EGT is a great indicator of a problem. I have set mine to warn me when it exceeds 900C.
This made me aware of a fuel pump problem at the track. After a number of laps my car would start to lean out due to the inadequacies of the stock fuel pump (couldn't sustain appropriate pressure for prolonged periods).

This is not something you could easily spot with and air/fuel gauge as on the overrun and under braking your A/F goes very lean and moves around a good deal.

I am not saying one should tune using EGT but it is a good feeling knowing that your EGTs are within safe levels -- especially after installing new parts or getting a new tune.

 

Some think a EGT warns you too late. I use aircraft egt probes. Fast reacting and dependable. 2,000 hrs is about 100k miles. Good enough for me. Let me get to the point. While at Thunderhill back in March, my egt's would climb to 1,700+ degrees on the front straight. Of course I would back out off it. Had I not had a gauge and stayed on the throttle, I would probably have a stroker kit by now.

For those who will flame me on the temps.
Probe is 1.5 in. from cyl. Spa gauge that has been calibrated.
Temps that high only on race fuel map. Not using it till I can re-map it.
I have had oil analysis that shows wear due to fuel and dirt ingestion(damn K&N). Engine is still fine.