1st generation Zipp hub recall

I also had my local bike shop send mine in for replacement.  Not much else to tell.  You definitely want to get this done before riding it though.  The flange ring on the defective hub can snap, which a) will almost certainly destroy the wheel and cause you to crash, and b) could damage your bike frame as well, since the spokes snap free.

They just replace the hub, not the entire wheel, as far as I know.

Didn't cost me anything.  I think SRAM is obligated to pay those costs because this was a mandatory safety recall under the Consumer Product Safety Commission.  However, I had to deal with them through my bike shop -- they probably handle these wheels in batches.