I just tried my code tonight here online (Wednesday, 11/17 @ around 9pm EST) and IT WORKED! (I have xbox360 in case you were wondering which console.) I was one of the ones who tried their codes shortly after Rock Band 3's release only to have it not work. So, good news (for me at least). I hope the rest of you have success too with this.
What a crazy ride.
BTW, downloading the license code takes only 1 second. But downloading the Lego Rock Band export track pack is another story. It didn't allow me to download in the background and play a game while downloading. That option didn't show up. Not sure why. It also did not download the 1.28 GB track pack very fast. That was my experience.