I use the REI Trail 40, which despite its name works really well for traveling. In fact, I just returned from a three-week trip to Spain where I stayed in in at least 9 different cities, so I did a lot of schlepping about on planes, trains, and buses. The pack performed just great. (I should also admit that I carry a packable daypack with me, so perhaps I'm not a 'true' one-bagger.)

The pack is a panel loader that's comfortable for me to carry for long periods of time. It has a decent amount of space and some nice side pockets, but it isn't as over-designed as some packs I've seen. One thing the pack doesn't do is maximize the amount of usable space based on airline carry-on specs compared to bags like the Patagonia MLC or the Tortuga Outbreaker. However, personally, I prefer a sleeker design which I think is more comfortable to carry for long distances. It also allows me to use the bag for hiking or short backpacking trips, which I wouldn't want to do with a boxier design.


Edit: I just noticed that the pack is on sale for 50% off on the REI website. Less than $60 for this pack is a really good deal, considering how expensive some of the competition is.