More I look at it, more sold I am on the Retina Book Pro.
The optical drive on my 2006 MBP (still using....) broke in 2008 and I haven't missed it one bit. Optical bay would be nice for extra storage, but for anyone who is going to blow past 512/768 (like me), you're going to end up with external hard drives sooner or later, and a 1TB optibay, though definitely convenient, won't help avoid the problem.
My _guess_ is that the RAM/SSD _isn't_ soldered on/permanently wedged in, because that would be, uh, ridiculous, and add an utterly unnecessary step to the production process. Of course Apple isn't going to broadcast that you can make the upgrades yourself when they can nail you for $200+ right away. Never have, never will.
Oh, and until they make a thunderbolt television (......) HDMI is an absolutely great addition.