It hit on Tuesday's patch and it's the pre-cursor to Cataclysm. It appears that it will count toward LoreMaster if you're working on that. (Horde has a similar event but not near Gnomer)

I'm a bit behind in knowing exactly what the event entails and how to be a part of it - but I just wanted to drop a note that it's out.

You'll get an in-game mail inviting you to go to Ironforge to see the Tinker Master (he stands on the little bridge with the spinning wheels in Tinker Town in Ironforge) and he sends you to Kharanos. So far, that's as far as I've gotten.

Here are some links I found that have more information:

http://www.wow.com/2010/09/07/operation-gnomeregan-and-zalazanes-fall-events-now-available/

This video says it shows you how to do the event- I haven't been able to view it yet so my apologies if it's a load of horse hockey.

You should definitely do this. It doesn't take long but is really fun. Make sure your music is on too. I did it on the PTR and will do it live tonight or this weekend for sure.

The event was fun. Took about 45 mins to an hour to complete.

1 tip-- when you finally get to the Operation Gnomeregan quest (after doing the pre-quests) you might end up standing around for a bit of time around the helipad waiting for the quest guy to come back. He leads teams into the battle (you don't have to be in a party to finish it, just be there and kill stuff) as groups. He will give you instructions when he appears and you can turn in your letter. Once you turn in the letter given from the pre-quests (see video in my post above) you will wait up to 5 minutes for the battle to begin. From there, just kill stuff and follow the crowd.

Don't go INTO Gnomer tunnels when you get to that part or you might cause the event to crash - wait outside the tunnels and let the trogs come to you before going inside after. You will probably see players telling everyone to "wait outside, don't go in" and what they are doing is trying to make sure the event doesn't bug out.

It was a fun event