From what my marketing and logistics roommate once told me, Apple likes to under promise and over deliver. Haven't had to get anything repaired through Apple to confirm their process or procedure, but he says that Apple is strives to beat its own estimates on repairs and such and hence uses overnight shipping when it comes to repairs.
Despite sending mine Monday and getting confirmation about receiving my nano on Tuesday, nothing on the Apple repair status page about mine shipping or even being approved! Still says "November 15, 2011: Product replacement pending." I really hope they don't disqualify my iPod just because I removed a battery that was swollen and dangerous. Should've taken pictures...
Also, good to see we're getting nice and shiny refurbs. The amount of entitlement in the thread with the original story about the nanos was ridiculous and aggravating. How Apple does battery replacements has been pretty well documented for a while: You get a refurb that is nicely polished and almost good as new. They reuse the parts that they can and replace the ones they can't and just stick them in new cases. Simple.