I use the Brain Bag and a vertical Brain Cell clipped in that I use extensively for international travel. I rarely remove the whole Brain Cell unless I want to use the Brain Bag for traveling about without the laptop once I arrive at my destination. Going through airport security is a snap: just unzip the back main compartment, open the Brain Cell and slide out the computer. No need to unclip anything.
If you want to remove the Brain Cell, it takes all of 30 seconds or less to unclip it and pull it out.
The pack swallows an enormous amount of stuff. You need to be careful. I find that it helps to have a few pouches or plastic file containers to hold your stuff in the main compartments. I haven't tried the Freudian Slip...someday, maybe. The front pockets are sufficient for smaller items, from pens to small notebooks, cell phones, etc. I have a steel/black Brain Bag and tied red paracord through the zipper pulls. It helps me to see that the zippers (black on black) are closed.