I ended up purchasing this bag for my recent trip to Thailand. Here's a mini-review for anyone considering this bag.
First, it truly is as light as the specs say it is. The Samsonite suitcase I had been using weighs about 16 lbs, which severely limits the amount of gear I can add before hitting the 50 lb airline maximum. With the new bag weighing under 5 lbs, I can cram in another 10 or 11 lbs of gear and still be fine. On the way back, we were able to fit two complete sets of gear (two sets of open-foot fins and booties, two reg setups in soft travel cases, two moderately heavy BCDs, a save-a dive kit, two 3/2 wetsuits, two mask and snorkel sets, and a flashlight or two) and clock in around 49 lbs.
Went I originally went to look at the bag at REI, I was expecting it to be made of fairly flimsy material, given the need for light weight. But it's actually a bit more robust than I expected. Certainly not as tough or thick as you would find in a premium suitcase, but after a total of 7 flights to and around Thailand, it's held up fine. The wheel assemblies aren't as sturdy as I would like to see, but so far no issues with them.
Now for the one major negative: there is no rigid handle or spine in this bag. That's what allows it to fold up on itself for easy storage in a hotel room or liveaboard, but it also makes it more difficult to pull. Rather than being able to balance the bag on its wheels and use only minimal effort to pull the bag, you end up holding up a decent amount of the bag's weight as you pull it. For short distances, this is fine, but I wouldn't want to have to drag this bag across town.
Related to the above, I can't recommend this bag for anyone who just wants to pack just clothing. Because there's no rigid spine, the bag would likely sag in the middle and make it even more difficult to pull. Scuba gear is fine, as the fins and the BCDs provide plenty of support.
So in summary, I really like this bag for it's intended use of getting two sets of dive gear to our various travel destinations. It's especially useful for liveaboards, where storage space for luggage is not always available. I think there are better options out there for non-divers who are looking for a large-capacity suitcase for clothing.
James