I've been using packing cubes and other organizers for years and I love them. I have a combination of eBags and Eagle Creek stuff. I bought some of the cheap brands initially and they fell apart after 2 or 3 uses, so I decided to upgrade to the "better" brands.
I like eBags' cubes a lot (and I also use their luggage and lunch boxes), but Eagle Creek makes other cool stuff besides just the cubes, and I get a lot more everyday use out of that stuff. I have a set of the Pack-It Sacs, and I regularly use the small and extra-small ones in my purse. They're water resistant, so I put my portable charger and cable for my phone into one when I go to the parks, in case it rains. The Small size is big enough for my Kindle as well, so I switch them out depending on if I'm carrying that or not. I also use the Pack-It Shoe Sac for carrying my sneakers on after-work gym days, since its water resistant lining also contains nasty shoe odor quite well.