[trip style = packing light]
Light luggage is so hot right now.
Seriously though, not only has luggage become more feather-like for ease and simplicity, but also in response to the continuous shrinkage of airline weight allowance.
Sub-O-G One line of luggage leaving all others in the dust is International Traveller's Sub-0-G rolling suitcases--the world's lightest suitcases. Their smallest 21" upright carry-on (20.5" x 14.4" x 7.6") weighs a mere 4.84lbs, compared to 8-12lbs for most other "light" suitcases! This size fits in most airlines' overhead bins and allows 20lbs of packing weight if you adhere to the 25lb carry-on weight restriction observed by most airlines. The cost isn't heavy either, I saw the carry-on sized bag on sale for $69 Canadian dollars in Vancouver. On the web the price varies.
Verdict - To Buy or Not to Buy I love the World's Lightest Sub-O-G line of suitcases, yet the feather-like nature of the bag comes with pros and cons. The 21" carry-on suitcase (referenced and shown above) is light and fairly enduring for self-use. Would I check this bag? No. Even though the bag is made using a fiberglass structure, aircraft material and durable nylon; I would not trust it with most airlines' checked baggage handling procedures--or lack thereof.
All in all, I love the concept and innovation and would recommend the 21" upright bag for carry-on use, but would not recommend the 24" or 28" upright suitcases because the sizes are not carry-on friendly and would have to be put under the plane. For now, I will stick with my hard-shell suitcase anytime I check a bag.