Spectrum displays like the Icom has look real neat but that's about it.
I have sat in front of an IC-756 Pro 3 for HOURS in contests on 80 meters and I probably never looked at the spectrum display after the first 10 minutes.
It never had any effect on what I found, or could hear to work.
Spectrum displays and panadapters are overrated as a useful feature in my opinion.
We are however visual creatures so it does have a lot of visual appeal to help sales.
I have an IC-7600 with the built-in spectrum display (band scope). Here are some of the ways it has been useful to me:
* I check the activity on an entire band with one glace.
* During contests I use it to help find an opening to call CQ as well as find stations when S&P
* When working a pileup I see how wide it is and watch the "ebb & flow". This helps me choose a frequency and know when to transmit.
* I can see regular noise patterns and how often they repeat across the band
* One of the coolest times was a month or two ago... I was listening to a dxpedition on CW when they said QSY 12M SSB. So I hit the 12m button, then hit the button to see the whole band on the scope and waited. The band was relatively quiet, so I just watched and waited. Up popped a signal. I tuned to them and was the first one to make contact - no waiting.