This is a really neat feature. My friends and I often times play "guess the gear" on the Horde toons we pass during our PvE adventures. We solve our arguments by looking them up in the armory, but now we'll just be able to right click on the Horde character's portrait and choose "Inspect." Pretty nifty.
Now... the real question becomes, where could this lead? For a long time players have been wondering if one day we'll be able to group across factions. Blizzard has obviously been leaning towards cross faction interaction and friendly support for a while now. We had the AQ gates opening, the recent goings on in the Isle of Quel'Danas, and lots of quests where you have to help out a member of the opposing faction.
What is significant about the ability to look at player's gear across factions is that it shows there are in game mechanics to allow cross faction communication and play. Before, all we could do was /wave /laugh /dance and trade through the AH. Now, we can literally look at what our 'enemies' are wearing, and what the details of those armaments are.
While I don't think Horde and Alliance will be grouping anytime soon, one cannot ignore the evidence that slowly but surely things are at least headed towards that conclusion.
What do you think about this new feature? Think this might be a (albeit distant) precursor to cross faction support and game play?