Since this is AMAZINGLY showing back up, I'll reiterate what I said earlier. The Done button was muscle memory for me. The way I saw it, if I needed new muscle memory, why not take it as an opportunity to try out Capture One. I did and I am glad I made the switch. Capture One processes RAW files so much better than Lightroom can. The difference is staggering at times.
That being said, if people are still griping about it a year later, it wasn't muscle memory anyway and who cares at this point? It's gone and has been for a year.