As someone who appreciated the DVD drive because it could be removed and the space/connector used to install a second 2.5" hard drive, I see the removal of the DVD drive altogether as a negative.
This combined with on-board RAM and on-board SSD storage... are any of the components in these new retina display MacBook Pros replaceable?
Yes, I barely used it. The only thing I used the bay for was a secondary 1TB disk alongside with a primary SSD - which makes a good combination for data intensive development. Guess this option is now gone as well ...