I’ve found travel underwear to be a big waste of money. On my last trip, I took those & just plain cotton - the cotton cleaned better and dried quicker (plus, they were cheaper in the first place). Save your money.
Packing cubes, though, are genius. Anything in the world can fit into a packing cube.
Sadly, though, for any trip more than 3 or 4 days, I need to bring too much liquid to just have a carryon.
I did this for a 3-week trip to a few European countries. It worked pretty well in terms of space, and there were fewer wrinkles than with folding, but it’s not by any means a magical solution.
I did, of course, bring too many things. Next time, 1 pair of pants and three shirts.
I was a travel agent for many years, so I can PACK like crazy. I always roll, because it’s the most efficient use of space. Small items get poked into odd corners here and there, as well as into shoes. I’m not that worried about wrinkles, because I pretty much hang everything up right away and iron before I get dressed anyhow. I’m not much for roughing it, so I really don’t go anywhere I can’t use an iron. My idea of camping is no mint on my pillow! 
When my parents travel, she puts her shoes inside his, then puts socks inside her shoes. Oh, and if they fly and they have enough stuff for two suitcases, they put half of their clothes/shoes in each bag, so if one bag is lost, neither is without ALL their clothes.
Gah, the 3 oz. max liquids rule just chaps my ass, because it is nothing more than “security theater”. I NEVER checked a bag for any trip less than 10 days. Not anymore, alas. So the bare essentials go in carry-on – contact lens solution, face wash, face toner, moisturizers, deodorant, toothpaste, a few other things – and everything else goes in checked luggage, in Ziploc bags to ward off leakage.
I also always carry on my makeup, toothbrush, jewelry, and camera, plus at least one full change of clothes and several changes of undies/socks, a sleep shirt and/or robe, plus another pair of shoes, and my bathing suit if I’m going someplace where I might swim. I do this for two reasons. One, I think it sort of wards off Murphy’s Law and the travel gremlins, and two, if my entire wardrobe is gone, including shoes, I’m screwed. I’m a fat woman with big feet, and I can’t reliably find clothes or shoes that will fit just anywhere.
If it’s a long trip I just UPS my stuff ahead, then I don’t have to carry it. Life’s too short to worry about saving every possible buck. Also, since I do a lot of travelling with costumes, armor, swords and what not, i don’t get hassled by security.
However, for short weekend trips, I take the pants I’m wearing, a couple of shirts and some chonies packed in a small valise.
Last time I flew I checked my bag, and then noticed all the people who think that a bag is considered carry on just because it has wheels. So they get up to the gate and have to be shuttled off to the side of the boarding ramp to have a groundcrew person take their bags and stow it elsewhere. How nice for them they get special handling for their bags that is free. Or if the passenger think it fits in the over head and I in my seat get to watch them struggle and shoulder it up above their heads and mine to push it in an overhead bin. Here’s hoping that latch stays shut.
Though I did feel a little smug when the folks with the too large carryons had to wait at the ramp in the blowing cold for their bags to get retreived.
If they airlines want to charge for baggage I have no problem with that, I also think they should charge for babies too, none of this lap crap.
Some people do this to get their luggage checked for free but others simply don’t know that their bag won’t fit. My go-to carry on bag fits in that nifty “Does your bag fit here?” box that tells you if your bag qualifies as carry-on but I’ve ended up on flights where my bag didn’t fit in the overhead compartment. I’d like to see something when you buy your ticket where it tells you the plane size and the largest possible bag that can fit in their carry on section. That would prevent a lot of the problems they have with bags not fitting on the plane properly.
I sometimes fly with a 21" roller bag which qualifies as a carry on and fits quite nicely in the overhead compartment (I used to check it a lot anyway, until the airlines started charging me to do so). Every so often, presumably because the flight was undersold, American would decide to change the plane to a smaller one (which would mean I no longer would get the seat I had selected, but that’s another story entirely); the smaller plane did not have the same overheard storage when we were boarding they would collect the roller bags at the door of the plane and put them into a rack which would then be put into the cargo part of the plane. When we arrived at our destination, the rack would be sitting by the door of the plane as we deboarded so you could collect your bag as you got out.
Generally I wouldn’t find out about the change in planes until I was getting my boarding pass. But even if I was informed of it earlier, I was never told that I would have to check a bag that would otherwise have qualified as a carry on.
Looking at them online, they seem to be like mini-suitcases that go into your larger suitcase. Why is this helpful when packing?