I just got QL the day before Emperor v4 was released.
Here are 3 Impressions/Experiences from just my 1 Day of Quantum Limitless, Stage 4.
(yup, I always start at stage 4, and then downgrade) 
Because SC subs are unleashed when taking action, QL4 had easy opportunities to show quick effects with my routine activities.
(1)
I use Text-To-Speech most of the time for reading, and play simple games like Sudoku in the background to keep myself from getting bored.
On QL, I felt the speed to be too slow, had to increase the rate by a couple levels.
… About 75 words/minute faster.
Plus, I didn’t need to play videogames. I could stay focused.
(2)
During my thinking/planning session, I decoded ALL productivity. 
I could write a book on this, suffice to say that what seemed like separate Goal Achievement, Productivity, or LOA Systems, all came together into a simple executable structure for myself to use.
And I started a Kanban board to apply it for my goals, but haven’t yet started the Evening Journal as intuited.
(3)
A note about the Feel of QL4 vs that of Limitless v2.
On Lv2, I felt like I had 10 points higher IQ. All emotional noise would be calmed down because I automatically saw how to handle everything. I simply thinked more clearly.
QL4 had more “Subconscious Coach” feel to it - like we have with S&S or PCC.
I had thoughts about how to respond to several situations, along with some awareness of why that was the right move in that moment.
That’s it for now.
Once I stacked it with Emperor v4, I too was groggy and discovered the loudness issue.
Now, I’ll run Ev4 exclusively for a few days and report on the Early Impressions thread.

Same here. It’s only 3 days for me though, so can’t make any claims.