The pack it system is awesome. I can pack 7 sets of undergarments (t-shirts, underwear, socks (2 long, 5 no show socks) full cube set, and only takes up 1/5th of my 21" suitcase. I basically went to Western / Eastern Europe with one 21" suit case and backpack (washing clothes once per week for 3 weeks).
This review was written in the old system and had content requirements that are different than reviews written today.