I seriously used to despise this addon. That's because it came out late Legion and suddenly I'm not getting invites, since I only ran Arcway once a week. Having a tool to measure one's aptitude so late in the expansion made no sense to me.
It began to grow on me in BFA. More times than not if you're group had high IO scores you would make the timer. I came back late BFA and knew I would have to grind out my score so I wouldn't get rejected. My intention was to only get to around 2000 so I could get invited to 15 keys no problem so I could get my chest.
But for some reason....I kept on pushing towards 16, then 17, up to 20. I never had any interest in pushing past 15 in Legion, sure I would do a 16 if that's the key that was available to us, but if it didn't provide higher loot then why bother with the extra difficulty?
It finally dawned on me....it's the TOOLTIP! Yes, when I randomly mouse over people or came across people with a 2.5k rating that was a solid purple "I wanted it". Then when I see people between 3K-4K, nevermind people in the Legendary orange percentile. It essentially gives off that Vanilla WoW feeling of prestige. No transmog, you take a look at someones gear and you know they're likely badass.
I find myself joining groups on my healer just because the scores are high and wanting to see what kind of numbers the DPS can put up, what manuevers and routes the tank will take. What strategies they implement.
Blizzard should consider showing both Arena Rating and IO Score on one's mouseover tooltip. It could put that fire under people again. ^