This thread has pushed me over the fence whether or not to get a business suitcase with a lock.

Originally I had most of my valuables in my backpack with a carry on. I carry a couple electronics, cash, IDs, etc. I tend to dose off during the flight. Although I don't think I've lost anything yet (if I did, I haven't noticed), I had been debating if I should get a locked suitcase (with convenient top access), but I'm happy I made the change. I can put my stuff in the overhead without really worrying much now (unless someone steals my overhead suitcase I guess [!!!]).