I'm on my third license, and I've never been audited or even contacted. I keep my paperwork up to date and honest, so no worries even if I was called.
When folks I'm talking to ask about the C&R, most are really worried that if you have a C&R you'd be the first to have your guns confiscated if it ever really comes to that. My answer is to stop being paranoid, because if it ever really comes to that, we've all got much bigger problems to deal with.
The C&R is a great tool. Fill out the paperwork, send the BATFE $30.00 and a few weeks to months later you get a piece of paper that lets you make a phone call, order a firearm and a few days after that the Big Brown Truck pulls up and give you another toy. It's awesome.