Finding the right luggage it not easy.  I just survived my own personal luggage hell.  I have always been particular about my luggage.  When I'm going to be spending every day for the next year with a bag, I get downright passionate about it.  Every time that I go on a trip, shopping for luggage is the one thing that stresses me out and generally drives me nuts. 

The Gorilla Test ==> Can this pack survive being tossed around by a 600 pound gorilla?  I'm very, very tough on luggage.  Cheap packs won't even survive the daily abuse of being tossed around or stuffed in a locker.  At some point on this trip I will attempt to stuff three times as much stuff into the pack as it was designed for.  Very few packs will survive this abuse.  Eagle creek makes a pretty good pack.  I can eventually destroy one, but it will survive for a good long trip.  Tumi makes great luggage, but their luggage is designed for business travel not for slumming around the world.  North Face makes good adventure gear.  I figure that if a pack is built for rock climbing - tough enough to handle being slammed against rock faces, it will survive anything I will do to it. 

The One Shoulder Test ==> The pack needs be small enough to take carry on.  I use the one shoulder test - if a pack fits comfortable casually thrown over one shoulder then it is a good size and weight. 

The Full Pack Theorem ==> Your pack needs to be small, tiny even.  It is not okay to bring a large pack that is only half full.  The "Full Pack" theorem states that travelers quickly fill any size of pack that they bring with them.  If you travel with 35 liters you'll have a very full 35 liter pack that you can still throw over one shoulder.  If you bring a half full 80 liter pack you'll soon be struggling with a pack that you can barely lift onto a train.

The Shot Put Test ==> The pack should have a good handle.  You won't often need to throw your pack, but there are those times when you need to toss it into a moving train or heave it towards shore before jumping yourself.  For the most part the handle is just a nice way to move the pack around a room or lift it into the overhead bin. 

The Clothes All Over The Floor Of The Train Station Test ==> The pack should be front loading.  If the pack is top loading you will occasionally need to dump all of your gear and clothes on the ground to find what you need. 

The Suspension Test ==> This is a new one for me.  You don't need a good suspension to carry your bag from the train to the hostel.  On this trip I'm planning on making it to Nepal and trekking up to the Base Camp of Everest.  This is a three week trek (Two weeks up and one week down).  For this trip at least, I need a "real backpack".  One with comfortable shoulder straps and hipbelt for weight distribution. 

The Goth Test ==> Finally, I like my pack to be simple black without a lot of external pockets or straps.  Black does a great job of disappearing into the shadows.  A black pack tends to give the appearance of being cheap and nondescript.  I might be wrong, but I think that someone will steal a red or blue backpack before stealing the black pack. 

After much deliberation, I bought the "Trash Can" pack made by North Face.  Yes, that it the real name.  It's black, according to the sales person it'll survive a hurricane without a scratch well washed and cleaner from the experience, it's 2600 cubic inches (that's just a bit bigger than a day pack), and it has a good handle.  Unfortunately, it's top loading, but since it's a great pack otherwise, I'm willing to live with that.