Someone can spend enough time to see how things are getting valuated with a lot of logging in and out. What would be useful is showing those scores because then you can find better items based on the scoring. You have tabulations showing ILVL difference and then state that it isn't just ILVL that matters. Then why do you have a disproportionate "compare ilvl" interface if it doesn't matter that much?
It is confusing / not obvious if two classes equip identical items (even if class 1 is a Prot Paladin equipping all DPS cloth items, and class 2 is a warlock) if they'll have the same gearscore.
It is also not obvious why someone's gearscore is considered higher than someone else's. Hunters are a rather prime example of this, since on any decent DPS spreadsheet / calculator certain items yield tons and tons of overall DPS while others don't. Some items are for longer fights, others are burst.
Someone putting on a bunch of junk high ILVL (or even pvp) items easily tops the gearscore even though the gear for their spec/build sucks.
Great tool, just chipping in egotistically towards what I think would make it even better!