I have been using a Colcasac for a few weeks and recently used it on a 2 week vacation, coupled with the Crumpler Gypsy Moth Flight bag.  I've noticed that the Colcasac has gotten a little looser than when it first arrived.  It is a snug fit and I like it.  It fit well into my bag and traveled well.  
During airport screenings, I just pulled the laptop in the Colcasac out and placed in the bin. It looks pretty nondescript while protecting the exterior. It adds very little bulk as well.
I was impressed with my Gypsy Moth Flight bag as well. It fit under the seat well in airplanes, carried all my necessities and had a great accessible but somewhat hidden zipper pocket for tickets and my wallet. I also like that the bottom is waterproof.
	
		
			
		
		
	
				
			During airport screenings, I just pulled the laptop in the Colcasac out and placed in the bin. It looks pretty nondescript while protecting the exterior. It adds very little bulk as well.
I was impressed with my Gypsy Moth Flight bag as well. It fit under the seat well in airplanes, carried all my necessities and had a great accessible but somewhat hidden zipper pocket for tickets and my wallet. I also like that the bottom is waterproof.
 
 
		 
 
		 
			 
			 
			 
 
		