No, it's not entirely a non-issue. I currently have the 2.3GHz 8GB model and almost all of the time, when I go into Mission Control, for example, it takes a sec for Mission Control to appear properly. Once it's done with a particular set-up, I can go back and forth to and from Mission Control and everything is super snappy. However, once I get to the point where apps are in different places because Mail goes from one space to another and maybe I open another browser and put it in full-screen mode, the lagging "re-sets", so to speak.
Scrolling on certain websites will also at times cause it to trip up a little bit, but not often. Again, it's very subtle and while it may be a non-issue to a lot, if not most, people, the fact remains that it's there.
On August 1, Apple started allowing the "entry-level" MBP w/ Retina Display to upgrade the CPU and amount of Flash, besides the RAM. My OCD has forced me into immediately ordering the 2.6GHz and 16GB of RAM, once I found out I could BTO a 2.6 model for only $100 more. I wonder if it will make any difference at all with this "lag issue", although the power user in me is doubtful. The reason I'm even remotely giving the additional RAM and 300 extra MHz any credibility at all is because the lag is SO subtle, SO quick, and perhaps the upgrades will just make a subtle enough difference to help with the lag issue. (no, I'm not upgrading because of the "lag issue")
Then again, it might just be the GPU that's responsible for drawing and re-drawing Mission Control, in which case even the i7 Extreme Edition wouldn't make a difference, not that Apple offers it to begin with. Unfortunately, there is no way to upgrade to 2GB of GDDR5 VRAM on the NVIDIA GT650M, not even in the high-end model. I say that because the 1GB of VRAM is constantly near capacity, according to iStat Menus.
EDIT: I just watched the YouTube video in the post before this one and if you look in the comments, this person actually has the 2.6GHz/16GB RAM configuration that I was talking about. Another observation I would make is the fact that he/she doesn't have that many apps open. But I'm intrigued. I'll clone my SSD to the new MBP and will make a true apples-to-apples comparison. OS X is really good when here is extra RAM it doesn't need. It uses it for caching I think and like I said, one of the aforementioned scenarios might just do the trick.
Edited by Crunch - 8/6/12 at 10:17pm