I love packing cubes, this is my second set.  I use these whether I am packing a carry on bag, or whether something larger to check in.  I travel alone about 75% of my time and i need to be as hands free as possible.  Using the packing cube allows for me to sort by outfit, casual or dress, or dirty and clean when returning from my trip!  I plan my outfits by day, try not to over pack options, plan on re-wear and roll my clothes to fit them nicely.  I have been known to do a full week travel with a carry on and a backpack!  I did 2 weeks in India with a medium roller bag I checked and a backpack, and I would never have been able to do it without the help of my packing cubes.  If you are not using them, you should be!