Oink is one of the buzzier social location iPhone apps to have launched in recent months, being the first app from former Digg exec Kevin Rose’s new incubator Milk. It went live on 3 November, so how is it doing?

Well, Rose says that it has notched up more than 100,000 downloads, with 100,000 items (restaurants, albums, films etc) having been added and rated by users. A new rating is posted every four seconds, and there have been nearly one million user sessions to date.

“We’re pretty happy,” he tells TechCrunch. “There are services out there that tell you Disneyland is awesome, but nothing tells you which fries are good. If we can win there and help people make purchasing decisions or decisions about what to do with their time, that’s huge.”

One thing that we’ve noticed about Oink is that it’s received two updates so far: one and two weeks after it launched. That indicates that Milk is planning to aggressively roll out new features for the app in response to feedback from those early users.

The question now is how to build a viral effect beyond that first 100,000 users, against competition from a host of other social/local/ratings apps. Rose’s history has been key in getting Oink onto the phones of early adopters, but this kind of app will be most powerful when mainstream mobile users – people who’ve never heard of Digg – are using it.