I've sailed on 14 RCL cruises, and admittedly miss the Concierge Lounge access. However, the Diamond lounges aboard the Freedom and Oasis class of ships are quite nice. Furthermore, RCL offers a Diamond "happy hour" aboard all of its ships now which is an enhancement for ships that did not formerly have a Concierge or Diamond Lounge. I think the way they've done it is sensible considering the number of Diamonds that are out there now.
We sailed aboard Mariner of the Seas just over a month ago, and really enjoyed the nightly Diamond event.