Last night I was having a discussion with one of my favorite pallies about Gearscore. He informed me that he had the add-on, and having heard so much about it in the blogosphere, but never having witnessed anyone actually using it on my server, we started a discussion about the tools one can use to estimate the gear of other players.
See, I don't use Gearscore, though I certainly don't have a problem with it. If I'm trying to put together a raid, and I want an estimate on others' gear, I use wow-heroes. This gives me a pretty good idea of the content for which they are prepared gear-wise, and it's also a very solid interface for quickly determining if they have put forth the effort when it comes to A) Enchants, B) Gems and C) Sons of Hodir rep (oh yeah, I went there.)
But in a daily pugged heroic, I don't bother with this. I have a slightly more ingrained way of determining someone's "Gearscore", and it's called... your health bar.
It wasn't something I intentionally began doing, but truthfully, I spend so much time staring at your little green-light-indicator, that it just became a natural thing for me. Note that I did not equate someone's health bar with their ability. But if a DK tank walks in with 50k health, I know he's probably got some pretty purple gear... or at least a LOT of Stamina gems (which is probable).
I'm a Disc Priest with somewhere between 20-22k health when buffed for a five man. If the elemental shammy in my pug has 16k health, I know he's starting out his gearing effort.
Because Stamina scales with item level on gear, your health pool tells me everything I care about in regards to your gear.
The thing is, I really don't mind quick gear estimation tools. To me, it's sort of like Recount. These things are tools to help you estimate some abilities or your gear. If used properly, they can be solid indicators. Yes, there are ways to fool the meter, just as there are ways to "fool" the gear estimation.
But it actually IS important for me to have a rough idea of your gear in a 5 man. I don't really care about your DPS to be honest - I'm sure you'll do fine, and if you are slacking, someone else can pick up what you lack. But I do need to know what your health is like. If you only have 16k health, then I may just keep you bubbled all the time in an effort to keep you from dying too quickly. I don't mind doing this - but I do need to know before hand if this is something I should be doing.